Legs are aching and veins are still fairly green two weeks after Sclerotherapy. Is this normal?

The body will actually absorb the veins with treatment and may take a few sessions. It is common to have bruising and swelling post sclerotherapy and you should be wearing compression for a few weeks. If you continue to have concerns, please follow up with your physician. Best, Dr. Emer

In general healthy leg veins contain valves that open and close to help the blood return back to the heart. Venous reflux disease develops when the valves that keep blood flowing out of the legs and back to the heart no longer function causing to pool in the legs and leading to signs and symptoms like dilated veins that you can see close to the skin in your legs. There are other symptoms you may or may not present, too. If sclerotherapy is not giving you the results you are looking for, consider a vein specialist to re-assess your legs again using ultrasound to scan to determine if venous reflux is present. Factors that contribute to venous reflux include age, gender, family history, heavy lifting, pregnancies, obesity, and prolonged standing. Your physician can help you make informed health care decision on the best treatment for you according to the ultrasound results and according to your specific goals. If reflux is present, it might be the reason why sclerotherapy is not working now and there are other options you can discuss with your physician about type of treatments. 
Best,

Retained coagulum can cause this discoloration as well as pain. Make sure you see the treating doc for guidance. Make sure you use the following topicals to reduce likelihood of hyperpigmentation of the overlying skin. 
You need to use some adjunctive measures after sclerotherapy to reduce post inflammatory hyperpigmentation. it is those that don't follow such instructions immediately following sclerotherapy, starting on day1 (next day) that seem to get retained hyperpigmentation. I recommend 2 creams: Scleroquin plus and Sclerovase and also Scler-X supplement to reduce post inflammatory hyperpigmentation (see link below) as well as compression stockings for at least 2 weeks.
H Karamanoukian MD FCS
certified vein specialist from ABVLM and double board certified surgeon

Following sclerotherapy the veins will usually become darker and the larger veins more so than the smaller ones.  This is due to trapped blood within the vein.  Usually this trapped blood will be reabsorbed by the body. I usually wait 6 weeks and then evacuate the clotted blood is it is still present.  If there are a lot of darkened veins then I have the patients come back for evacuations at 3 weeks post treatment. Following sclerotherapy, some veins will dissolve immediately, some will take about 6 weeks and some will not dissolve and need additional treatments.

It isn't unusual for the legs to ache several weeks after sclerotherapy.  This is usually because the vein is hardening and your body is reacting to this.  Over a period of weeks to months your body will break down and absorb the veins, and this can cause some intermittent discomfort.  I have found that wearing compression stockings and taking anti-inflammatory medication helps greatly.  I recommend getting the legs rechecked especially if there are areas that remain dark or tender.  Sometimes with larger veins, there may be parts of the vein that do not close completely and need retreatment.  This may be what you are seeing on your legs.