The term "black color option" refers to a choice or preference for something in black, typically when referring to products such as clothing items, vehicles, electronics, etc. Full definition
It will be available only in Black color option. (phoneradar.com)
The phone is available in champagne gold and midnight black color options as well as pearl white and pink. (nashvillechatterclass.com)
Finally, there are rumors claiming a new color variant (slate gray) is joining the white and black color options of the second - generation Pixel phones. (ibtimes.com)