When I try to create a gold material and I put the same color in the reflection swatch, the reflection turns out green. It looks like a negative value is returned.
Why is that?
the screenshot attached has one with background and one without.
Try to set the “Energy preservation mode” parameter in the Options rollout of VRayMtl to “Monochrome” and see if it helps.
Best regards,
Vlado
yeah great! that helped. Any idea why it does this?
Is this going to affect physical accuracy?
It helps if you think of the VRayMtl material as a layered one; since the reflection layer reflects away more of the red and less of the green light, you only get some green light and most of the blue light to pass through reaching the underlying diffuse layer.
Best regards,
Vlado
that explains 
thx Vlado
Also, bare in mind that the “diffuse” component of metals is close to black. Setting the diffuse color close to black will also help, and keeps the shader closer to reality.
Best regards,
A.
So most of the color of metal is caused by the reflection color? I’m always having a hard time creating convincing metals
Good tip! thx.
Yes, same as glass. Only with glass you use the fresnel reflection, and the amount is almost white.