Yeah, if you just noticed it, your doc should see it.
Having blue veins on your breasts or anywhere else is quite normal for light skinned individuals of any age.
The term "blue blood", meaning aristocrat, comes from the middle ages. Wealthy people no longer had to work out in the fields in the sun. Being indoors most of the time they didn't tan and their blue veins could be seen through their pale skin, hence they were the "blue bloods".