Clarify please - IPL targets the melanin color not the hair color?

The answer to your question is a little complicated. Laser hair removal picks up on the melanin in hair, so it's more effective on darker hair.  IPL will target both melanin and pigments in hair dye. But dying blonde or gray hair darker does not make IPL more effective. This is because the dye does not get all the way down to the root of the hair; damaging the root of the hair is what causes the permanent hair reduction. In dyed hair, the dyed portion of the hair will burn off, but the actual root of the hair is not affected. Electrolysis is more effective on light-colored hair, but is very time consuming. 

IPL can be used for hair removal. In our office, we prefer the Yag laser for hair removal. Coloring the hair shaft will cause the IPL to pick up the pigment, but the color will not penetrate into the hair follicle, the ultimate target of laser hair removal. Best, Dr. KaramanoukianLos Angeles

You have posed in excellent question.  Unfortunately light hair is very difficult to remove with lasers or other light sources.  Applying dye to the skin's surface does not allow for presence of dye in the hair follicle and therefore does not improve the effectiveness of laser or IPL treatment with regard to hair removal.