diff --git a/.changeset/fair-panthers-learn.md b/.changeset/fair-panthers-learn.md
new file mode 100644
index 0000000..f825b0d
--- /dev/null
+++ b/.changeset/fair-panthers-learn.md
@@ -0,0 +1,5 @@
+---
+"@sardine/colour": minor
+---
+
+feat: Add isHexColour
diff --git a/.changeset/nervous-ears-burn.md b/.changeset/nervous-ears-burn.md
new file mode 100644
index 0000000..74a35ad
--- /dev/null
+++ b/.changeset/nervous-ears-burn.md
@@ -0,0 +1,5 @@
+---
+"@sardine/colour": minor
+---
+
+feat: Increase coverage of different CSS RGB formats
diff --git a/.changeset/rude-parrots-press.md b/.changeset/rude-parrots-press.md
new file mode 100644
index 0000000..4fda232
--- /dev/null
+++ b/.changeset/rude-parrots-press.md
@@ -0,0 +1,5 @@
+---
+"@sardine/colour": minor
+---
+
+feat: Add isCSSRGBDarkColour
diff --git a/.changeset/slimy-drinks-invent.md b/.changeset/slimy-drinks-invent.md
new file mode 100644
index 0000000..dda7f3e
--- /dev/null
+++ b/.changeset/slimy-drinks-invent.md
@@ -0,0 +1,5 @@
+---
+"@sardine/colour": minor
+---
+
+Add isCSSRGBColour
diff --git a/.changeset/spotty-pears-confess.md b/.changeset/spotty-pears-confess.md
new file mode 100644
index 0000000..41a51e6
--- /dev/null
+++ b/.changeset/spotty-pears-confess.md
@@ -0,0 +1,5 @@
+---
+"@sardine/colour": minor
+---
+
+feat: Add isCSSNamedDarkColour
diff --git a/src/assertions.ts b/src/assertions.ts
new file mode 100644
index 0000000..fddcdd0
--- /dev/null
+++ b/src/assertions.ts
@@ -0,0 +1,16 @@
+import {
+  cssRGBARegex,
+  hexRegex,
+  hexAlphaRegex,
+  shortAlphaHexRegex,
+  shortHexRegex,
+} from "./util/regexers.js";
+
+export const isCSSRGBColour = (colour: string): boolean =>
+  !!colour.match(cssRGBARegex);
+
+export const isHexColour = (colour: string) =>
+  !!colour.match(hexRegex) ||
+  !!colour.match(hexAlphaRegex) ||
+  !!colour.match(shortAlphaHexRegex) ||
+  !!colour.match(shortHexRegex);
diff --git a/src/converters.ts b/src/converters.ts
index 13450ac..799d8de 100644
--- a/src/converters.ts
+++ b/src/converters.ts
@@ -1,7 +1,7 @@
 import type { LabColour, NamedCSSColour, RGBColour, XYZColour } from "./types";
-import { constrainLab, linearRGB } from "./util/index.js";
+import { clamp, constrainLab, linearRGB } from "./util/index.js";
 import { namedCSSColours } from "./util/namedCSSColours.js";
-import { cssRGBA, hexAlphaRegex, hexRegex, shortAlphaHexRegex, shortHexRegex } from "./util/regexers.js";
+import { cssRGBARegex, hexAlphaRegex, hexRegex, shortAlphaHexRegex, shortHexRegex } from "./util/regexers.js";
 
 /**
  * Converts sRGB colour space to XYZ.
@@ -71,8 +71,11 @@ export function convertRGBtoLab(colour: RGBColour): LabColour {
  * @returns - An hexadecimal string 
  */
 export function convertRGBtoHex({R, G, B, A}: RGBColour): string {
-  const hex = (n: number) => n.toString(16).padStart(2, '0');
-  return '#'+hex(R)+hex(G)+hex(B)+(A ? hex(Math.round(A * 255)) : '');
+  const hex = (n: number) =>{
+    const value = clamp(n, 0, 255);
+    return value.toString(16).padStart(2, '0')
+  };
+  return `#${hex(R)}${hex(G)}${hex(B)}${(A ? hex(Math.round(A * 255)) : '')}`;
 }
 
 /**
@@ -81,23 +84,51 @@ export function convertRGBtoHex({R, G, B, A}: RGBColour): string {
  * 
  * - `rgb(0,0,0)`
  * - `rgba(0,0,0,0.4)`
+ * - `rgb(0 0 0)`
+ * - `rgba(0 0 0 / 0.4)`
  * 
  * @returns {string} - An hexadecimal string 
  */
 export function convertCSSRGBtoHex(colour:string): string {
-  const match = colour.match(cssRGBA);
+  const rgb: RGBColour = convertCSSRGBtoRGB(colour);
+  return convertRGBtoHex(rgb);
+}
+
+/**
+ * Converts CSS RGB colour format into RGB colour object.
+ * @param {string} colour - A CSS RGB colour in the format:
+ * 
+ * - `rgb(0,0,0)`
+ * - `rgba(0,0,0,0.4)`
+ * - `rgb(0 0 0)`
+ * - `rgba(0 0 0 / 0.4)`
+ * 
+ * @returns {RGBColour} - RGB colour object. 
+ */
+export function convertCSSRGBtoRGB(colour: string): RGBColour {
+  const match = colour.match(cssRGBARegex);
   if (!match) { throw new Error(`convertCSSRGBtoHex expects a valid CSS RGB string but got ${colour}`)}
   const rgbNumber = (n: string) : number => parseInt(n, 10);
   const alphaNumber = (n: string) : number => parseFloat(n) ?? undefined;
-  const rgb: RGBColour = {
+  return {
     R:rgbNumber(match[1] as string),
     G:rgbNumber(match[2] as string), 
     B:rgbNumber(match[3] as string), 
     A:alphaNumber(match[4] as string)
   };
-  return convertRGBtoHex(rgb);
 }
 
+/**
+ * Converts an hexadecimal colour into RGB colour object.
+ * @param {string} hex - An hexadecimal colour in the format:
+ * 
+ * - `#000`
+ * - `#102030`
+ * - `#ffff`
+ * - `#102030ff`
+ * 
+ * @returns {RGBColour} - RGB colour object. 
+ */
 export function convertHextoRGB(hex: string): RGBColour {
   if (typeof hex !== "string") {
     throw new Error(`convertHextoRGB expects a string but got a ${typeof hex}`);
diff --git a/src/getSRGBLuminanceFromHex.ts b/src/getSRGBLuminanceFromHex.ts
index f797815..7b55379 100644
--- a/src/getSRGBLuminanceFromHex.ts
+++ b/src/getSRGBLuminanceFromHex.ts
@@ -1,5 +1,5 @@
 import { convertHextoRGB } from "./converters.js";
-import { linearRGB } from "./util/index.js";
+import { getSRGBLuminanceFromRGB } from "./getSRGBLuminanceFromRGB.js";
 import type { WCAG } from "./types";
 
 /**
@@ -13,15 +13,8 @@ import type { WCAG } from "./types";
  * https://www.w3.org/WAI/GL/wiki/Relative_luminance
  * @param colour an hexadecimal colour
  */
-export const getSRGBLuminanceFromHex = (
-  colour: string,
-  standard?: WCAG
-) => {
-  const isWCAG21 = standard === "WCAG2.1";
+export function getSRGBLuminanceFromHex(colour: string,
+  standard?: WCAG) {
   const rgbColor = convertHextoRGB(colour);
-  const r = linearRGB(rgbColor.R, isWCAG21);
-  const g = linearRGB(rgbColor.G, isWCAG21);
-  const b = linearRGB(rgbColor.B, isWCAG21);
-
-  return 0.2126 * r + 0.7152 * g + 0.0722 * b;
-};
+  return getSRGBLuminanceFromRGB(rgbColor, standard);
+}
diff --git a/src/getSRGBLuminanceFromRGB.ts b/src/getSRGBLuminanceFromRGB.ts
new file mode 100644
index 0000000..a065867
--- /dev/null
+++ b/src/getSRGBLuminanceFromRGB.ts
@@ -0,0 +1,25 @@
+import { linearRGB } from "./util/index.js";
+import type { RGBColour, WCAG } from "./types";
+
+/**
+ * Returns the relative luminance of a colour in the sRGB space.
+ *
+ * The calculations are compatible with WCAG 3.0 as it aligns with the sRGB spec
+ * and difference to WCAG 2.1 is minimal in a 8 bit channel.
+ *
+ * https://www.w3.org/TR/2008/REC-WCAG20-20081211/#relativeluminancedef
+ *
+ * https://www.w3.org/WAI/GL/wiki/Relative_luminance
+ * @param colour an hexadecimal colour
+ */
+export function getSRGBLuminanceFromRGB(
+	{ R, G, B }: RGBColour,
+	standard?: WCAG,
+) {
+	const isWCAG21 = standard === "WCAG2.1";
+	const r = linearRGB(R, isWCAG21);
+	const g = linearRGB(G, isWCAG21);
+	const b = linearRGB(B, isWCAG21);
+
+	return (0.2126 * r) + (0.7152 * g) + (0.0722 * b);
+}
diff --git a/src/index.ts b/src/index.ts
index 5147a07..da37b53 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -10,5 +10,9 @@ export {
 } from "./converters.js";
 export { RGBdistance } from "./RGBdistance.js";
 export { getSRGBLuminanceFromHex } from "./getSRGBLuminanceFromHex.js";
+export { getSRGBLuminanceFromRGB } from "./getSRGBLuminanceFromRGB.js";
 export { pickHexColourContrast } from "./pickHexColourContrast.js";
+export { isCSSRGBColour } from "./assertions.js";
+export { isCSSNamedDarkColour } from "./isCSSNameDarkColour.js";
+export { isCSSRGBDarkColour } from "./isCSSRGBDarkColour.js";
 export { isHexDarkColour } from "./isHexDarkColour.js";
diff --git a/src/isCSSNameDarkColour.ts b/src/isCSSNameDarkColour.ts
new file mode 100644
index 0000000..ebdd4b8
--- /dev/null
+++ b/src/isCSSNameDarkColour.ts
@@ -0,0 +1,17 @@
+import { convertNamedCSSColourtoHex } from "./converters.js";
+import { isHexDarkColour } from "./isHexDarkColour.js";
+import type { NamedCSSColour, WCAG } from "./types";
+
+/**
+ * Evaluates if a named CSS colour is dark by measuring the contrast ratio against black and white
+ * @param {string} name - A named CSS colour, ie: `hotpink`
+ * @param {"WCAG2.1" | "WCAG3.0"} standard - Evaluate agains "WCAG2.1" or "WCAG3.0"
+ * @returns {boolean | undefined} Returns `true`, `false` or `undefined` if name is not a valid CSS named colour
+ */
+export function isCSSNamedDarkColour(name: NamedCSSColour, standard: WCAG): boolean | undefined {
+  const hex = convertNamedCSSColourtoHex(name);
+  if (hex) {
+    return isHexDarkColour(hex, standard);
+  }
+  return undefined
+}
diff --git a/src/isCSSRGBDarkColour.ts b/src/isCSSRGBDarkColour.ts
new file mode 100644
index 0000000..54c1be1
--- /dev/null
+++ b/src/isCSSRGBDarkColour.ts
@@ -0,0 +1,14 @@
+import { convertCSSRGBtoRGB } from "./converters.js";
+import { getSRGBLuminanceFromRGB } from "./getSRGBLuminanceFromRGB.js";
+import type { WCAG } from "./types";
+
+export function isCSSRGBDarkColour(colour: string, standard: WCAG): boolean {
+	const rgb = convertCSSRGBtoRGB(colour);
+	const colourLuminance = getSRGBLuminanceFromRGB(rgb, standard);
+	// We know white luminance is 1 so we can pre-calculate the whiteLuminance to 1.05 (1 + 0.05)
+	const whiteContrast = 1.05 / colourLuminance;
+	// We know black luminance is 0 so we can pre-calculate the blackLuminance to 0.05 (0 + 0.05)
+	const blackContrast = colourLuminance / 0.05;
+
+	return whiteContrast > blackContrast;
+}
diff --git a/src/isHexDarkColour.ts b/src/isHexDarkColour.ts
index 869e7c5..df265c0 100644
--- a/src/isHexDarkColour.ts
+++ b/src/isHexDarkColour.ts
@@ -7,7 +7,7 @@ import { WCAG } from "./types";
  * @param {"WCAG2.1" | "WCAG3.0"} standard - Evaluate agains "WCAG2.1" or "WCAG3.0"
  * @returns {boolean} Returns either `true` or `false`
  */
-export const isHexDarkColour = (colour: string, standard: WCAG): boolean => {
+export function isHexDarkColour(colour: string, standard: WCAG): boolean {
   const colourLuminance = getSRGBLuminanceFromHex(colour, standard) + 0.05;
 
   // We know white luminance is 1 so we can pre-calculate the whiteLuminance to 1.05 (1 + 0.05)
@@ -16,4 +16,4 @@ export const isHexDarkColour = (colour: string, standard: WCAG): boolean => {
   const blackContrast = colourLuminance / 0.05;
 
   return whiteContrast > blackContrast;
-};
+}
diff --git a/src/tests/assertions.test.ts b/src/tests/assertions.test.ts
new file mode 100644
index 0000000..e26548a
--- /dev/null
+++ b/src/tests/assertions.test.ts
@@ -0,0 +1,36 @@
+import test from "ava";
+import { isCSSRGBColour, isHexColour } from "../assertions.js";
+
+test("assert true if string is in the CSS RGB format", ({ is }) => {
+  is(isCSSRGBColour("rgb(12, 23, 111)"), true);
+});
+
+test("assert false if string is not in the CSS RGB format", ({ is }) => {
+  is(isCSSRGBColour("zzz( 23, 111, 87)"), false);
+});
+
+test.skip("assert false if string doesn't have 3 colour values", ({ is }) => {
+  is(isCSSRGBColour("rgb( 23, 111)"), false);
+});
+
+test("assert true if string is a short hexadecimal colour", ({ is }) => {
+  is(isHexColour("#333"), true);
+});
+
+test("assert true if string is a six digital hexadecimal colour", ({ is }) => {
+  is(isHexColour("#333000"), true);
+});
+
+test("assert true if string is a short hexadecimal colour with alpha", ({
+  is,
+}) => {
+  is(isHexColour("#333f"), true);
+});
+
+test("assert true if string is an hexadecimal colour with alpha", ({ is }) => {
+  is(isHexColour("#333000ff"), true);
+});
+
+test("assert false if string is not a valid hexadecimal colour", ({ is }) => {
+  is(isHexColour("#333HH0ff"), false);
+});
diff --git a/src/tests/converters.test.ts b/src/tests/converters.test.ts
index c6058ba..9d868bb 100644
--- a/src/tests/converters.test.ts
+++ b/src/tests/converters.test.ts
@@ -198,6 +198,46 @@ test("converts CSS RGBA format to hexadecimal colour with alpha channel", ({
   is(convertCSSRGBtoHex(RGBA), expectedHex);
 });
 
+test("converts CSS RGBA format to hexadecimal colour with short alpha channel", ({
+  is
+}) => {
+  const expectedHex = "#ffffff80";
+  const RGBA = 'rgba(255,255,255,.5)';
+  is(convertCSSRGBtoHex(RGBA), expectedHex);
+});
+
+test("converts CSS RGB format to hexadecimal colour but clamps max channel value at 255", ({
+  is
+}) => {
+  const expectedHex = "#ffffff";
+  const RGBA = 'rgba(300,500,900)';
+  is(convertCSSRGBtoHex(RGBA), expectedHex);
+});
+
+test("converts CSS RGB format to hexadecimal colour but clamps min channel value at 0", ({
+  is
+}) => {
+  const expectedHex = "#000000";
+  const RGB = 'rgb(-300,-500,-900)';
+  is(convertCSSRGBtoHex(RGB), expectedHex);
+});
+
+test("converts CSS RGB with space separated values to hexadecimal colour", ({
+  is
+}) => {
+  const expectedHex = "#ffffff";
+  const RGB = 'rgb(255 255 255)';
+  is(convertCSSRGBtoHex(RGB), expectedHex);
+});
+
+test("converts CSS RGBA with space separated values and forward slash for the alpha channel to hexadecimal colour", ({
+  is
+}) => {
+  const expectedHex = "#ffffff80";
+  const RGBA = 'rgba(255 255 255 / 0.5)';
+  is(convertCSSRGBtoHex(RGBA), expectedHex);
+});
+
 test("throws an error if not passing a valid CSS RGB format", ({
   is,
   throws,
diff --git a/src/tests/isCSSNameDarkColour.test.ts b/src/tests/isCSSNameDarkColour.test.ts
new file mode 100644
index 0000000..eadcef6
--- /dev/null
+++ b/src/tests/isCSSNameDarkColour.test.ts
@@ -0,0 +1,15 @@
+import test from "ava";
+import { isCSSNamedDarkColour } from "../isCSSNameDarkColour.js";
+
+test("verify if `darkblue` is a dark colour", ({ is }) => {
+  is(isCSSNamedDarkColour("darkblue", "WCAG2.1"), true);
+});
+
+test("verify if `lightgoldenrodyellow` is a dark colour", ({ is }) => {
+  is(isCSSNamedDarkColour("lightgoldenrodyellow", "WCAG2.1"), false);
+});
+
+test("return undefined if named colour does not exist", ({ is }) => {
+  /* @ts-ignore-line */
+  is(isCSSNamedDarkColour("rose", "WCAG2.1"), undefined);
+});
diff --git a/src/tests/isCSSRGBDarkColour.test.ts b/src/tests/isCSSRGBDarkColour.test.ts
new file mode 100644
index 0000000..0ac3e39
--- /dev/null
+++ b/src/tests/isCSSRGBDarkColour.test.ts
@@ -0,0 +1,10 @@
+import test from "ava";
+import { isCSSRGBDarkColour } from "../isCSSRGBDarkColour.js";
+
+test("verify if `rgb(20, 20, 20)` is a dark colour", ({ is }) => {
+  is(isCSSRGBDarkColour("rgb(20, 20, 20)", "WCAG2.1"), true);
+});
+
+test("verify if `rgb(200, 200, 200)` is not a dark colour", ({ is }) => {
+  is(isCSSRGBDarkColour("rgb(200, 200, 200)", "WCAG2.1"), false);
+});
diff --git a/src/util/index.ts b/src/util/index.ts
index 85e7cfd..5ebcb59 100644
--- a/src/util/index.ts
+++ b/src/util/index.ts
@@ -109,3 +109,14 @@ export function constrainLab(n: number): number {
 
   return t;
 }
+
+/**
+ * Clamps a number between two values
+ * @param {number} value - The value to be clamped
+ * @param {number} min - The minimum value
+ * @param {number} max - The maximum value
+ * @returns {number} - A clamped value
+ */
+export function clamp(value: number, min: number, max: number): number {
+  return Math.min(Math.max(value, min), max);
+}
diff --git a/src/util/regexers.ts b/src/util/regexers.ts
index 12c20e1..be00fe6 100644
--- a/src/util/regexers.ts
+++ b/src/util/regexers.ts
@@ -7,4 +7,4 @@ export const shortHexRegex = /^#[a-fA-F0-9]{3}$/;
 /** Four digit Hexadecimal colour, ie: #FFF4 */
 export const shortAlphaHexRegex = /^#[a-fA-F0-9]{4}$/;
 /** CSS RGB with optional alpha channel, ie: rgb(23, 213, 11) or rgba(12,34,12,0.2) */
-export const cssRGBA = /^rgba*\(\s*(\d+)\s*,\s*(\d+)\s*,\s*(\d+)\s*,*\s*(\d+.\d)*\)$/i;
+export const cssRGBARegex = /^rgba*\(\s*([-+]?\d+)\s*(?:,)?\s*([-+]?\d+)\s*(?:,)?\s*([-+]?\d+)\s*(?:,*|\/*)\s*([-+]?\d*[.]?\d+[%]?)*\)$/i;