Adding heather color variant

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).