Yes, with a Diffuse Node. However, the veins MUST be in the exact same places on both the Displacement map, AND the Diffuse map.

Valandar, Would I have to paint the veins on top of the displacement map in Photoshop and then save that layer by itself? If so where would that difuse node connect?

No, you would save it as a different map... What I would reccomend, is to load in the Displacement Map and the Texture Map both into Photoshop, with the Texture Map as the upper layer and the Displacement Map as the "Background. Next, I'd reduce the opacity of the Texture Map to about, oh, say 40% to 60%, whatever is clear enough to see through. Then, with a VERY LIGHT touch of the airbrush, on a new third layer, trace over the veins on the Displacement Map, fading them into the skin where the veins end. Then, make the "Texture" layer opaque once more, flatten the image, then save. It would go right where you have the existing texture map.

If you use a Component node to colour the output from the displacement image blue (for example) and a Blend node to mix it with the skin texture, you should be able to overlay the veins on the diffuse input by using the same black and white texture without having to load a new coloured map. Bill

Or you could use the Displacment map as Alpha in a Blender node to mix some color into the texture map. You probably want to run the displacment map through some math nodes to adjust the contrast. Stefan

Both Quinlor and williamshell are right. I was just trying to come up with a way that requires less experience with the Materials Room