Hewlett Bryan notes: 

>>I have used saturated tartrazine in 70% cellosolve as a counterstain to PAS 
for over 35 years. The solution is much more stable than Metanil yellow. 
Martius yellow is an excellent alternative, as is an alcoholic solution of 
Picric acid. I know, I know!!! All you safety minded people stay OFF my 
back!<<

Tartrazine (C.I. 19140) is the infamous F.D.C. Yellow #5, the food additive 
without which junk food as we know it would not be possible. This odd fact 
may account for the rather ominous warning labels I've sometimes seen on 
containers of tartrazine for laboratory use. It would appear to be a minimal 
risk laboratory chemical.

It's an Article of Faith in Alternative Medicine that F.D.C. Yellow #5 is the 
Great Satan of junk food, or one of them at any rate, though I think the 
evidence here is fairly minimal. Perhaps the most convincing accusation - 
probably not very convincing - is that it has something to do with the 
obstreperous wiggliness of small boys.

I have a yarn about Martius yellow (C.I. 10315) too, but it probably doesn't 
belong in this thread (arrgh!)

Bob Richmond
Samurai Pathologist
Knoxville TN