Are there differences in appearance between coronary arteries and veins?

YES. Coronary arteries and veins appear very differently. Coronary arteries thick walled have a whitish to pink color and are larger than coronary veins. Coronary veins smaller thinner and bluish in hue. Hope that answer helps.
Yes. Yes, the coronaryveins are thin walled vessels like all veins. The arteries are thicker, muscular walled structures as the coronary arteries actively dilate and contract in response to cardiac demands and various signals. In many instances, the coronary venous structures travel right next to the arteries.