The tan lines are made via color node & separate tan image, but I learned that if you have gamma correction on, it won't work, I asked BB if he can help cause I only have Poser 9, which doesn't have GC.  and can't test them. He said he would but apparently hasn't had time,  so for now I'll just use what I have & warn customers to turn GC off.

Newer versions of Poser have several ways to use GC, especially involving the image map, before rendering corrections. You will not have access to those hooks in your material room. So, users with GC enabled should manually set the GC for any black&white process node/channel maps, like trans/bump/displace/spec/blend node B&W maps/etc, to 1.

Example: http://i.imgur.com/yzW27kn.jpg

If one doesn't manually set GC, "1" in the case of these sorts of maps, Poser will apply default GC to the image. This can cause B&W maps to grey out or become undefined, resulting in bad transmaps for hair, bad overlays, etc..  One can also use Scenefixer to do this, but it's easier and often less troublesome to just go through one's nodes by hand, making the correct adjustments.

PS - You could get someone to do this for you, in a later version of Poser, then simply upload the corrected Material Pose room files to a Free section for "GC-enabled Poser users."