fix(colors): alpha channel is now used if rgba is used

Previously the alpha channel was ignored and the opacity setting was
used instead. Now the alpha channel will be used if specified.

Closes react-financial#27

packages/charts/src/utils/colors.ts

@@ -1,11 +1,15 @@
 import { colorPresets } from "./colorPresets";
 
 export const colorToRGBA = (inputColor: string, opacity: number = 1) => {
-    if (inputColor.charAt(0) === "#") {
+    if (inputColor.startsWith("#")) {
         return hexToRGBA(inputColor.trim(), opacity);
     }
 
-    if (inputColor.indexOf("rgb(") !== -1 || inputColor.indexOf("rgba(") !== -1) {
+    if (inputColor.startsWith("rgba")) {
+        return inputColor;
+    }
+
+    if (inputColor.startsWith("rgb")) {
         return rgbToRGBA(inputColor.trim(), opacity);
     }
 
@@ -31,6 +35,7 @@ export const rgbToRGBA = (inputRGB: string, opacity: number = 1) => {
         throw new Error(`invalid inputRGB: ${inputRGB}`);
     }
     const [, r, g, b] = res;
+
     return `rgba(${r}, ${g}, ${b}, ${opacity})`;
 };