Why doesn't the food coloring do anything?

So I have tried dying my hair with food coloring. The ends of my hair are bleach blonde so it would show up. I have tried just food coloring by itself, food coloring mixed with conditioner, food coloring mixed with developer. None of them work. Instead of a bright blue I just get a really pale green on the ends of my hair -.- Why doesn't the food color stick like its supposed to? But I've researched it online and it is actually possible to dye your hair and lots of people have successfully done it.