A light reduction is all that is needed to get these colors to develop. Turn down your oxy a bit until you get a small, bushy flame. Pass your work in and out until you get the colors you want. The colors pop almost immediately. Let it cool a bit, then go back to a neutral flame. Chagall has deeper blues, but you can get a bright, metallic blue finish, and also have iridescent rainbow in spots, depending on how long it is worked.