I do have background in chemistry. . . Not much 
but it's there. (*laugh*) One thing that occured 
to me as I read Keys's message is that brown and 
*especially* yellow paints often have sulfur 
compounds in them. These seem to be rarely to 
never used in other colors that are towards the 
reds and blues in the color spectrum.

Perhaps there's something behind this? (*shrug*)

Many Sharp Smiles,
--Drac