I wanted to share with you an experiment I have been doing - we have been talking about this sort of thing on the pitcher plant forum, but since it's a VFT, I thought I would post it here.
For the last few months, I have been adding blue food coloring to the water my test VFT sits in. It's in a 5 inch tall dixie cup (yes, with holes in the bottom) that sits in a small japanese ceramic bowl and the water level varies from 1/2 to 1 1/4 inches. Each time I add water to the bowl, I also add 3 drops of coloring.
Nothing has happened - it looks just my other flytraps. So, today I am starting a new approach. I just fed it a big fat fly and a large drop of blue food coloring in the trap!
We will see what happens......