Tummy tuck and belly button scar got darker - any help? (Photo)

Worth a try using 4 to 8% hydroquinones. If after a few months no lightening the you might have permanent hyperpigmentation. Sorry. As for doing liposuction on your abdomen I believe it would sculpt you more. 

Hello! Thank you for the question! It is common for scars to fully mature for up to a year. In the meantime, there are a few things that may help to ameliorate your incision/scar. The most proven (as well as cheapest) modality is simple scar massage. Applying pressure and massaging the well-healed scar has been shown to improve the appearance as it breaks up the scar tissue, hopefully producing the finest scar as possible. Other things that have been shown to add some benefit, albeit controversial, are silicone sheets, hydration, and topical steroids. These can usually be started at approximately 3-4 weeks postop and when incisions healed. In addition, avoidance of direct sunlight to the incision will significantly help the appearance as they tend to discolor with UV light during the healing process. Scars will never disappear, but attempt is made to make the finest scar in a concealed location. Incisions may be revised to lower or conceal better if enough laxity exists. If unsightly scars are still present after approximately a year's time, other things that your surgeon may consider are intralesional steroid injections, laser, or just surgical revision of the scar itself. Hope that this helps! Best wishes!

Another option for your belly button is to attempt to suture the stalk deep to the fascia so it invaginates and the dark pigmented skin is somewhat hidden due to the invagination.  A last resort is to wait a few years and re-advance the abdominal wall skin inferiorly, excising and closing the current umbilical keyhole and creating a new umbilical opening that is more aesthetic.