When to add colorant is a pretty flexible rule. Bright colors like the flourescents are probably best added pre-cooking, though I've added after cooking with no problems. I'll add what I think will be enough, a little on the conservative side if need be, before heating. After heating I shoot a bait and see how it looks. Single cavity molds are great for this, you only have 1 off color bait if the color isn't right! Adding colorant to hot plastic works well enough for adjusting the color. I'll also do something similar if I want to shoot 2 shades of the same color. Sometimes I might want to make a batch of light blue baits and a batch of dark blue. I'll start with light blue, shoot my baits, and then add more colorant and shoot the dark batch.
