On the E-commerce platform, the behavior right now is to delete invalid selections for products. For example, if you have a Red T-shirt that comes in sizes S-XL, and the same shirt in Green that only comes in sizes S-L, the XL selector totally deletes off the page. A better user experience would be to simply disable that option (front-end themes could make them more transparent, desaturated, etc.) This way, when a user is shopping around, and they need an XL shirt, if they stumbled into the green selection from a listing page, they would leave seeing that the shirt is only available in sizes smaller than Large. By disabling it, but still showing it, the opportunity is offered to instead subconsciously show the user that this shirt does indeed come in their size, just in a different color. Overall, increasing the chance for a product sale.