I'd guess a copper sulfate content w/o looking it up.
Laurel Mtn. will do that on occasion when you're laying on a first coat.
...A flash of copper on the steel in an area and no rusting because of it.
I've noticed it happens when the steel is warm. Or I needlessly go back over a spot that I've already covered and try to recoat it getting every little streak covered.
All this on the first coating on bare steel. Doesn't seem to occur or at least it doesn't effect anything (can't see it) after the blue has begun to build after a cycle or two.
Cool basement temps seem to work best for me when applying the stuff to avoid the copper plated look.
..Maybe the formula given in the book is incorrect. The amt of copper sulfate if it is in fact included may be too high. Just a guess there of course.
