I have very visible green veins on my legs. Can these be treated? (photos)

Green or blue leg veins are called reticular veins and the gold standard treatment for them is sclerotherapy.  You seem to have a lot of veins in the posted picture so you should consider seeing a vein specialist and having a venous ultrasound to see if there is any underlying reflux contributing to the vein formation.

When aware of signs and symptoms of venous disease, you should seek medical advice. There are  treatment options and conservative management available for handling the condition. If you become informed, this is the ideal way to prevent any aftereffect. 
I recommend a Board Certified in Veins and expert to explain options and manage vein disease. Thanks for your question!

Hi Elizabeth. The leg veins in the photo you send can be easily treated. However, you need an ultrasound scan to the deeper veins in your legs to ensure that no veins underneath the skin need treatment

These veins in the back of the thigh are either nonsaphenous tributaries or tributaries of the small saphenous system. Either way, you need to have a DUplex vein scan in an accredited vascular lab under the directionof a vein specialist and the decision can be made if you need ablation of the small SV in conjunction with sclerotherapy or sclerotherapy alone. See an ABVLM certified vein specialist. Dr H Karamanoukian

As doctor Landi wrote;Do dupplex ultrasound to rule out underlying truncal (GSV, SSV, etc) veins disorder, if negativeFoam sclerotherapy will clean up those veins nicely.Make sure to chose accredited vascular lab for dupplex and experienced, ABVLM-certified physician for your injection