could it also be that they've only figured how to make fast glide in white so far? assuming that due to it still being a relatively new material still to the production lines, it could be only producible in white. Likely, you're right though, it costs a fortune to get the materials for pads, Lefevre can't afford that at from an investment standpoint right now, they would lose thousands of dollars from how big a surplus of colored fast glide coated jenpro rolls/sheets they end up having.
Primo/Opti Slide was also offered in Black, White, and Grey the first year they had it, which was the Optik1s first year in the release cycle. I remember @TheGoalNet was able to get it in red on his old o1s before they stopped offering it at the time. I'm pretty sure during the gnetik 4s first year, they expanded it to the current color selection. Brians is naturally far more established than Lefevre currently is though, and could afford to have a surplus if they even were to end up having it. But, Primo was also sought after by Brians retail customers a lot, which led to the color expansion. It was also only offered out of high demand, and was expanded because of further demand, so they would probably have a very easy time making back the investment, whereas Fastglide is a new material Lefevre has promoted, and Speedskin back when they were partnered with CCM was a promoted material by them, not as much a demanded one like Primo/Opti Slide was.