Taking Lipitor (atorvastatin) for 10 yrs. Started eating vegan. My cholesterol dropped from 175 to down to 124. What are the risks of coming off lipitor (atorvastatin)?

Be seen. You should discuss it with your doctor. From a pure cholesterol standpoint, it sounds like you could, but your doctor may have other reasons to want to keep you on it.
No risks. When we are born, our 'bad' cholesterol (ldl) is ~ 50 mg/dl and so is the LDL of tribes that eat non westernized diets. If you are able to keep your LDL below 100 mg/dl - ideally close to 60-70 mg/dl (depending on what other risk factors you have) with a healthy diet and exercise, and never had a heart attack, you will not need lipitor (atorvastatin).
May have to try. You should not stop the medication without consulting with your doctor. They may or may not want to do this depending on your particular case. Other features of the lipid profile impact risk above and beyond cholesterol including hdl, LDL and triglycerides. Sometimes markers of lipoproteins are important also such as apob and LDL particle #. Your doctor can do this if necessary.