If you mean to change your text color on the signature, do this:
open this site
choose your color
copy the R;G;B dec (add , instead of ; ex. 255;255;255 should be 255,255,255
now if you want that color you copied to be your outline color paste it in stroke_colour= if you want that color to be "inside" of your text paste it in font_colour=
hope i helped