Altium & Patterned Colors
Maybe check out this stuff http://techdocs.altium.com/display/ADOH/PCB+Object+and+Layer+Transparency

and see here on the layers/view config window:


There is also this youtube video which shows how to set layer transparencies really easily, but you need Altium Designer 13 or above.

This is as close as I can find to help you, otherwise have a look at Mechanical Layer 1 for 3D objects and maybe find how they do the purple diagonal cross hatching to show 3D bodies in 2D mode.. maybe there is something you can take from those view options and apply them to your needs?