Growth medium coloring

[Robert Brambl]

Chuck Staben's good suggestion probably stems from another useful  
application of water-based culinary food colorings:  to stain growth  
media-agar plates and tubes in a genetics laboratory where it is essential  
to keep separated media of various compositions. These coloring agents are  
apparently harmless to fungi, or at least to Neurospora. 

One can also get a really intense and deep color effect for photography by  
combining several of these colorings.  

Alternatively, for a really dark effect, use India ink in agar; but use  
the real stuff, and not New Age substitutes that contain detergents and  
surfactants.

Best wishes.

Bob