Adding heather color variant

[WineLife]

What is the proper way to add heather color variants to clothing? As I've searched online all the advice says to search and click on "heather" as an option but I do not have that, just default solid colors. I can add the "Charcoal Heather" color variant for instance, but then there's still no appropriate selection for base color and pattern. Since these values are used for search I need to make sure its all correct, and I'm surprised there isn't a heather option. Any help is appreciated (I'm new).