OK, I've had some email traffic with Daniel on this. Here is a summary and proposal for a better solution:
LDConfig is meant to primarily be a shortcut for colors that exist in real LEGO plastic. It was extended to include colors that exist for purchase on Bricklink, but may not be plastic (such as this piece:
http://www.bricklink.com/catalogItem.asp?P=70496). It also contains some other physical (not a sticker / pattern) colors for completeness. It currently does not contain any colors for the sole purpose of making a sticker / pattern look more realistic. If we started down that path, LDConfig would grow to an unmanageable size and no longer be end-user friendly for choosing colors in MLCAD, Bricksmith, etc.
Therefore, I would like to propose (both as a SteerCo Member and ColorMaster) that a new standard be created to allow Patterned Parts to have custom colors inside the part file:
0 !COLOUR Metallic_Copper CODE 512 VALUE #E8905F EDGE #333333 METAL
The custom color would be required to use a color code in a new range block (say 512 to 1024). A color code in this range would not override any existing color codes. Software Tools would not be required to implement changes, but the standard would suggest that the custom color code would only have scope in the patterned part file.
I have tested this with LDView, which works and displays correctly. I also tested with MLCAD, which displays the part, but complains about it.
Thoughts?
Scott W.