I have problem with Genesis 9 strand based hairs. When I load a strand based hair and I load the material, I see in the viewport window the color change. The generation of starnds working perfect. But when I start the iray rendering the color of the hairs is white. Is this the problem because I'm using Daz Studio 4.21.05 or something else is the problem?
You'll want to check the different parameters in the Surfaces tab. The viewport usually only shows things like Diffuse and Gloss, but there are a lot of other parameters that go into an Iray render.
Look for things like Emission or Top Coat colors being set suspiciously bright, or Glossy Roughness being set to 1 instead of a decimal between 1 and 0.
Thank you for the advices! I'm think so the problem is not on the surface but may the version of the Daz Studio. I was try a few hair on same vendor hairs and I found perfectly working hair.