Check the how-to guide to add color: www.healingwell.com/community/mCode.aspx
We may be changing it eventually down the road, but we were experiencing a lot of strange code issues with the old signature box. I am currently testing different editors to see if we can come up with something else that works better.
To add color, look for the section that says "Font Color" and type the name of the color on each side of your text with the brackets. On the end bracket remember to add a backslash before the color name.