Clarification on a few things.
First, there are 3 different bases:
Small
Large
Huge
While the huge bases are sized the same, the center peg area is slightly different. This is because the epic ships have the number tabs built into the stand, while the Large base ships have it built into the base.
Second, I can think of two reasons for why no black. The first reason is that it might blend to the background too well, providing an unfair advantage to judging if a maneuver will clear or not.
But the second reason is a manufacturing reason. Black doesn't typically look good in a transparent plastic. It ends up looking like a smokey gray and kinda blah. So to do it properly, you'd have to change materials to an opaque plastic. This sounds simple enough, but each material will have different properties, including how much it shrinks during cooling. Since the bases all have to be the same size, a different shrink % would require the mold to be slightly larger. And since they're going to continue making non-black ones, that means a second mold needs to be created. This costs $$$. Furthermore, they now either need to run the mold in the machine in short bursts as productions needs are required, but this involves heft setup fees and machine down time as you swap between the two molds. Or, if they wanted to dedicate a machine to it, you then end up with downtime for that machine, which costs $$.
TL:DR - material changes require more money. Dye changes not so much.
