The uv light that this stuff enhances, or concentrates, is light we cannot see. Fish can. However, the light we can see is made up of certain colors that border right on the edge of that invisible light. Call it borderline uv light. The enhancer does such a great job that this borderline uv light becomes very visible to us under certain circumstances. This bluish-purple glow or ghost color that's seen when cover dips using the enhancer are applied to baits is proof that the enhancer has been added in an appropriate ratio to the plastic. The same amount will do transparent and light color plastics well too. More opaque colors like a heavy watermelon or pumpkin seed and solid colors can tolerate a wee bit more of the enhancer, but there you'll need to explore just how much is enough using a black light. Under black light if the solid baits have that bluish-purple aura, they have enough of the enhancer added.