You can do it via the text editor by typing \C[x] where x is a number from 0 to 7(?) corresponding to a color. Off the top of my head, 0 is black, 1 is blue, 2 is red and 3 is green. I don't know the others, but a quick google search should fix that.
You can also use the hexa codes if you need more colors. Example: <c=RRGGBBAA>your text</c>
RRGGBB is the hexa code (without the #) and AA is the opacity (in hexadecimal, from 00 to FF) .
For example, pink at full opacity would be <c=FFC0CBFF>this text is red</c>.
"FFC0CB" is the hexa code for pink and "FF" is 255 in hexadecimal
If you want to get even more advanced, you can use the <c2=XXXXyyyy>...</c2> command, where XXXX is the primary color and yyyy is the shadow's color . I think there's even an abridged version of that, but I can't remember what it is. Should be easy enough to google.
Check the wiki if you need!
If you want to get even more technical, there's a bunch of other stuff you could do using script calls, but it's probably not necessary!