Having issues with cover spray masks

[gbzh01]

Hi there
I am doing sunglasses and having two issues that drive me nuts. As we have a lot of spray masks in the industry, I don't get them exact in key shot.
- To get the spray mask, I do it as producing a sunglass, I double the surface in the CAD and put it to the front of the solid (maybe 0.05mm)
- Then I color the solid and the spray surface in key shot
Problem: Only appears with transparent frame and solid spray mask.
1. Even though I do a little distance between the two parts, I sometimes get ugly spots (see in the picture). How to get rid of those?
2. The coloring in the rendering is not correct. See the picture. Outside it's green and inside smoke. When you look at the temple inside, it should be a dark green but definitely not black. How to get it correct?
Thanks for any help.

[gbzh01]

OK, I got it. It's a mix of different things I learned in Webinar 43

[LayC42]

 In my experience there's no need for an offset surface. It's a label thing. A label with another material.

Do you need further help?

[bdesign]

Another suggestion would be to split the spray mask areas into separate surfaces with the Geometry Editor and apply a dedicated material. It looks like you've already figured out that you need to have Global Illumination enabled with at least 1 Indirect Bounce.

Cheers,
Eric