Re: why do some flower colors fade with vinagar gas and others do not?

Many colors in plants are caused by anthocyanins, which change colors 
depending on pH.  The vinegar "gas" will change the pH around the 
petals.  Anthocyanins are often the red and blue colors found in flower 
petals.  The greens and yellows are probably chlorophylls and carotenoids 
which are not sensitive, in the same way, to pH changes.  There's lots of 
info on the net under "Anthocyanin" if you do a search.  Good luck.


David Hershey, Mad Science Adminitrator adds:

A classic school exercise uses anthocyanins in red cabbage as a pH indicator:

http://www.madsci.org/experiments/archive/859332497.Ch.html