You can use [c=4]This is my text[/c=3] to make it fade from red (4) to green (3)...
If you want a list of colours, I recommend using HEX codes and finding a web page on the internet that shows a table of colours and their codes... To use hex codes would look like:
[c=#ff0000]This is my text[/c=#00ff00]
for the same colours
This site lists a lot of hex colours
