—”So WHITE isn’t a color ?”
There are different “COLOR SYSTEMS” and they work in different ways. Three, four, or more, depends on who you ask.
In easy terms, white is the presence of all colors and black is the absence of all colors.
And then there is composite black!
Composite black, the mixing of cyan, yellow, and magenta, almost makes black! Used on early inkjet printers.
A quick easy explanation:
https://www.colormatters.com/color-and-design/color-systems-rgb-and-cmyk
Now, if you really want to go into the rabbit hole...
Do a search on ‘white a color?’.
A fun side trip: Pointillism!
An interesting topic!