Warning: This api uses British variable names.
Warning: As yet untested.

RGB colours are tables formatted like so:
{red = 0, green = 0, blue = 0}

Functions:
mix(colourA table, colourB table, …)
returns table
This function mixes multiple colours, simply input them as tables.

mixCC(ccColourA number, ccColourB number, …)
returns table
This function mixes computercraft colours, input computercraft colours and a RGB colour is returned.

toCC(colour table)
returns number
Input RGB colour, output computercraft colour.

toRGB(ccColour number)
returns table
Input computercraft colour, output RGB colour.

Pastebin:
http://pastebin.com/8DipR5FQ
Enter "pastebin get 8DipR5FQ RGBUtils" into the terminal to install the api in the working directory.