I had Sclerotherapy about 5 years ago and have permanent bruising. Can it be tattooed over? (photo)

I don't see any contraindication to getting a tattoo to camouflage the brown areas.  These appear to be staining from your prior procedure.  It would be prudent to see a vein specialist to look at your leg before tattooing to ensure that all is ok with your venous circulation.

What you have is not bruising but hemosiderin deposits, along with possible post inflammatory hyperpigmentation. Hemosiderin is the iron part of the blood cells that stains the skin. It's very hard to get rid of. Looking at the pattern of the staining, you probable had multiple varicose veins where you had injections. There is higher risk of this happening if the concentration of the injection medicine is too high. You have a couple of options at this point--1. Find an experienced vein doctor, get and ultrasound and see if you have any residual veins with trapped blood. If this is present, you can needle them to express the trapped blood, and this can go a long was to reduce the staining. 2. Try laser treatments to lighten the staining. This is a difficult treatment, so I would suggest looking for a laser center with experience treating this condition.

Hello!  This is an unfortunate side effect sometimes after sclerotherapy for varicose veins.  It is more common if the internal disease wasn't treated before performing the injections into the surface veins.  It also occurs more often in patients who have more advanced venous disease such as hair loss, swelling, and darkening of the skin near the bottom of the leg and ankle.
I would recommend you see a venous specialist who can treat all aspects of vein disease for a new evaluation before proceeding with a tattoo.  If your skin is being damaged from untreated internal venous disease, a tattoo will not heal correctly and may actually be more prone to scarring or an infection.
There are options to treat staining with certain types of lasers, but your leg skin must be as healthy as it can be and there cannot be any untreated venous disease.  So please seek care from a vein care specialist in your area before proceeding with a tattoo.  They may be able to remove the brown staining so you won't need a tattoo!
Good luck!