Can you see veins on color doppler during breast ultrasound? i saw it on u/s image and asked and dr said normal, blood vessels in breast? nursing too

Yes: Yes, seeing blood vessels in the breast during ultrasound is normal. It is also true, that when nursing, the breasts are more vascular, because making breast milk takes energy, requiring oxygen, nutrients and water, all of which arrive via the blood. Focal areas of increased blood flow in the breast can have may causes, more often infection in a patient who is nursing.

Yes: A color doppler does show blood flow and does show arteries and veins. Since arteries and veins tend to have blood flowing in opposite directions, the color doppler will show this as a red or blue signal. The breast normally does have arteries and veins within it and these will increase during pregnancy and breast feeding. Your doctor was right.