I just discovered something pretty obvious: that with transparent enamel over silver, you are dealing with the colors of light rather than pigment.  This means that the primary colors are not Red, Yellow and Blue, but rather Magenta, Yellow and Cyan. 

I could never find a red that fired nicely over silver (except the Japanese 106B from Coral at Enamelwork Supply) but they don't make it anymore.  But I was cruising the net looking for a colorwheel to help with some other color problems, when I saw a 'light' color wheel, and a good true red exists midway yellow and magenta. 

  Thompson's old Raspberry fires screaming hot pink over silver (not my favorite color) I wondered if I fired it over yellow enamel or gold foil, would it turn red.

And it worked! As a bonus, it is a red that holds firing after firing, no yellowing, no clouding or problems. Plus, you can vary the tint from yellowish to purplish, just by adjusting the layers.  It is like having lots of different colors with two enamels.  So now I want to see if this also works with Cyan. 

This would simplify my workspace, but where to get a good magenta that fires over silver when I run out of Raspberry...All the ones I've tried from the Ninomya line fire Orange.  Nice orange, but still...so if anyone out there has a bottle of Raspberry they don't want, or some suggestions of reds that fire over silver, let me know. 

Lillian