The short answer is "maybe".
Custom thicknesses of our stock colors from Radical Rubber usually aren't a problem. Just drop us a line letting us know what color/thickness you'd like and we'll give you a quote on it. Typically there's a 5-yard minimum order on custom sheeting.
Polymorphe has been known to develop custom colors, but it's a lengthy and expensive process (or a quick and VERY expensive process). If you're serious about getting a custom color and have a budget of at least $100/yard, drop us a line at firstname.lastname@example.org