Food coloring?

[caiteydid]

This is going to sound like a funny question!  For a science project, I am testing to see if Sage prefers certain colors over others, and if she does, possible reasons for this.  I was originally going to buy some colored pellets to test the theory with, but when I went to get them I found that they're flavored- and that could majorly mess with my results!  So I was thinking about coloring her plain colored pellets.  First, though, I wanted to make sure food coloring wouldn't hurt her.  I know they use it to color the colored pellets, but I didn't know if that was special "bird safe" food dye.  I also know people use it to color toys, but generally parrots aren't ingesting toys.  I'm figuring it'd be okay, but better safe than sorry.

And with that in mind- do you guys notice if your birds have any color preferences (or... un-preferences)?  What are they, if you do notice?