This is a tough call - I have a strong preference for black, since my interior will not be stock, and will most likely be black. I also have a V8 so the shifter would be To decide between 3mm and 1.5mm I'd need to get an idea regarding durability of the thinner material. I'd probably pay $400-$450 for the thicker mat, or $300-$350 for the thinner mat, depending on which was offered.
My concern is that $300-$350 is still a pretty significant investment. I'd be hesitant to pay it if the thinner matt couldn't stand the test of time. If a thicker matt costs 25% more than a thin one, but lasts 150% longer, I'd consider it money well spent. If the thinner mat could take stand up to punishment almost as well as a thicker one, why go the extra mile (or millimeter, in this case). Does that make sense?
In short, I'm voting for the thick, black mat, but if the thin matt is still pretty rugged, I'd love to spend less!
As for color - black matches virtually everything. I think that, if you had to pick one, you'd please more customers with a black mat than a gray one. Since my truck is a hodgepodge of years, colors, and vehicles I don't think it would be a deal breaker, but I'd strongly vote black.
Either way, I'm fully confident that if you determine the juice is worth the squeeze, in this case, you will produce a quality product. Thanks for putting in the effort!