I have been playing happily for the last couple years with a combination of Thompson Enamels - 533 and 722. Ken Bova, I understand,  was responsible for discovering how beautifully these go together. When torched, 533 shows a range of marvelous colors (white, aqua, orange, purple, and more); if you then dip it in 722, the crackle effect is glorious. At a workshop recently, there wasn't enough of the plain colors and I mixed some robin's egg blue with my 533 and the results were fascinating, but wildly unpredictable (more so than usual) - some were glorious, most, well, not. I've tried some other experiments, mixing 533 with single colors, but most were not very successful and some were truly awful. Probably the best was about half 533 with Peacock blue and a touch of robin's egg and lavender. One expert suggested I apply 533 as a second coat, but the one experiment in which I tried that was really unpromising. 

Are there other colors that "do tricks" when heated?

Has anyone done experiments like these and made interesting discoveries? I'm all ears! My earrings are sculptural so I love colors that transform throughout the piece.