Hilary - Sounds like an odd response from them, but they don't usually do modifications to existing products that I'm aware of. They do offer a
1952-1953 Temperature Gauge as Original Chevrolet and GMC Pickup Truck that reportedly fits either truck. Yes, that one has a black face, but if you want the tan face, maybe just order their
earlier 1947-51 "Tan" decal kit and overlay the black face with the "Tan" decal? If the new tan doesn't match your older tan, you could use the rest of the decals to reface all of them so they match.

With the new temp gauge, you will still need to get some red paint (probably a modeling paint would do) and repaint the needle to make it match your other gauges. That is if your existing gauges have the red needles?
A couple others factor to consider are what engine your truck has and if you've upgraded to 12 volt or not? You didn't mention either of those details, and I couldn't find anything in your previous posts to answer those questions. They can play a roll in deciding what gauge you order.