Please don't accuse people you don't know and second guess their motives in a conversation with them.
>I've made cashew milk and oat milk at home and they're naturally colored as they are on store shelves
Which is neither here nor there. I didn't say all are colored white: I used the term "usually". Second, even naturally white "alternative milks" have artificial coloring added for when they hit the shelves for consistency etc (manufacturers that don't do that are glad to advertise it in the box).
Second, both are not milks. Milks are what comes out of animals mammary glands (even legally in most jurisdictions). Advertisers and "health product" peddlers hijacked the term (that existed for millennia) to mean "random juices".