Could someone share with me their ideas on how to color white fondant? I have some ideas but not sure if they are the best. I also don't want to buy the pre-colored fondant since I only need one color. thanks!

If you are making your fondant add it when you melt your marshmallows.

If you are coloring pre-made, knead your fondant to get it workable. Smooth it out into a disk and put a drop of two of color on top, put on some food safe gloves and rub it in, and start kneading. It's going to look a little marbled. Let it sit (well covered) for a few minutes and come back and knead it some more.

Definitely easier if you add it during the melting process though.