I used 1/2 cup regular sugar per color. I place 1/2 Cup of the sugar in a platic bag add 1 drop of your food coloring. I also prefer Americolor gel colors so Im not too sure how the liquid colors would work. If you want it darker add an other drop. Being careful not to add too much or you'll have liquid sugar.
Procede to mix and smoosh it around in the bag. Takes a few minutes. If you still see some lumpy color keep on mixing.
Once your done it should be relatively even in color.
You can place your colored sugar in back into a plastic bag or if you have empty sugar containers use those.
Feeling a little creative I decided to add a little liquid meringue to the sugar to make some Sugar cut outs. You could use these on a cake cookies or brownies. Fun project you could do with your kids too.