Removing the 5 o'clock shadow on the armpits?

I'm pale and have really dark coarse underarm hair, and nothing helped removing the green shadow on that area. The green shadow is shaped exactly where I usually have my hair growth. Shaving, waxing or epilating didn't help. I'm thinking of using an at home IPL (Silk Expert Pro 5 by Braun) to get rid of the 5 o'clock shadow on my armpits, will that be effective? Also, what is the exact cause of this green type of pigmentation? Thank you for reading.