Not too much, mind you. Just about half a bottle. (Really only 10 drops).
I just wanted to make sure that the muffins turned out bright green. The idea behind it was to make it like the Earth. Blue and green. I know. Some people are out there doing amazing things to celebrate Earth Day, but here we settle with making colored muffins.
Needless to say, they were enjoyed by one and all. Bug loved them since they were his favorite color. I had two very happy boys and one happy blueberry crumb eating cat. (My other cat, Scout, would never stoop so low as to eat human food).