It didn't work out very well. Perhaps just a hint of prussian blue glaze might do but I didn't stop there. Next thing I knew, I was in trouble with lots of blotchy blue. Ugh! So I'll give it all another go soon. A bit more reading, a bit more thinking, and then it's back for another round! :-)
A quote from Koo's book serves as a good reminder:
"A thin layer such as this will dry very quickly (within seconds, ideally) and allow successive layers to be soon added. While it may not seem a significant amount of paint, you can add literally dozens more layers within an hour. Soon it will accumulate to build up a convincing form and rich color. Scores of layers of thin, transparent color, ultimately adding up to create a luminous image. This is the beauty of egg tempera painting."