Yeah, it's mainly a sales-driven decision. Ford has phased out red options on several models due to lower demand. While red is a popular color in performance-oriented vehicles, it typically doesn't sell as well in trucks and SUVs compared to shades of black, white, gray, and blue, which dominate the market.
The plant itself (Kentucky Truck Plant) isn't the limiting factor since, as you pointed out, the Super Duty still offers red options. It's more about demand trends for specific models. If a certain color doesn’t move enough units, Ford may drop it to streamline production and reduce costs.