If you mix fluor. blue w/ orange or yellow you'll just get an ugly green... maybe it'll be fluorescent but it won't be yellow or orange once you mix the blue in.
The wax is supposed to turn from clear to white after a few uses. I hope this helps. :O)
I would have thought that mixing plenty of orange with a little floursent blue would give it the UV reactive properties needed as the floursent blue is a clear dye under normal light
Do you want it to be UV reactive orange or just a bright orange.
When you use fluorescent dye in your lava(ie: blue, green), you only achieve the specifically stated color if you use a black light on it. Otherwise under normal light conditions there is very little color given to lava by fluorescent dye. So if you took red lava and added some fluorescent blue dye to it, your lava will stay red under normal light. But if you shine a black light on the lava, it will appear blue. I wish there were neon dyes available for lava, that would solve your dilemma. As of now neon food colors are only available that color the liquid but not the lava.