color.js transform mix

[andij]

Is your feature request related to a problem? Please describe.

I'd like to use the mix function within chroma.js to transform colours.

Describe the solution you'd like

The capability of using design tokens to modify a colour with the mix function, described here: https://gka.github.io/chroma.js/#chroma-mix

Resulting in a token setup like this:

"error": {
  "value": "{ theme.color.error.value }",
  "modify": [
   {
     "type": "mix",
     "color": "white",
     "ratio": 0.9,
     "mode": "lrgb"
    }
  ]
}

Describe alternatives you've considered

Using the brighten function results in undesirable colours.

Currently the mix function works (with limitations), as the default ratio of 0.5 and the default mode of lrgb is being applied with this token setup:

"error": {
  "value": "{ theme.color.error.value }",
  "modify": [
   {
     "type": "mix",
     "amount": "white"
    }
  ]
}

It is currently possible to use alpha to achieve the correct outcome, but it relies on the background of the containing element to be white, which is not 100% predictable.

"error": {
  "value": "{ theme.color.error.value }",
  "modify": [
    {
      "type": "alpha",
      "amount": 0.05
    }
  ]
}