How to Fade Pigmentation from Laser Hair Removal?

Depending on the severity of the hypopigmentation, there may be some improvement with time - many months. If there is true depigmentation (complete absence of pigment), then there is no easy, reliable treatment. There are a number of ways to help PIH or post inflammatory hyperpigmentation such as what you have experienced after laser hair removal - chemical peels, topical bleaching creams with or without hydroquinone and exfoliating creams can all be helpful. Time helps healing also - remember to keep areas covered with sunscreen.

Before you spend $$ on peels or IPL, try these topicals.
This is called post-inflammatory hyperpigmentation (PIH). 
I recommend Melarase AM and Melarase PM creams from Kare Skin as well as a broad spectrum sunblock like Spectrase. Bothe are from Kare Skin. Scler-x post inflammatory hyperigmentation relief complex is a great supplement to take as well. See link below. 

Unfortunately, there is nothing you can do about post inflammatory hypopigmentation (whitening of the skin). In regards to hyperpigmentation, although at times, it can be permanent, often it will resolve with time. Some people try to treat this hyperpigmentation with bleaching creams to attempt to fade the marks. There are several different bleaching creams available but the most effective ones are prescription or dispensed through a dermatologist's office.