It's not color == distance though, it is color + brightness. Maybe there is some unknown principle at play but you could say that about anything which is not di

It's not color == distance though, it is color + brightness. Maybe there is some unknown principle at play but you could say that about anything which is not directly measurable, for example how old the earth is. But, it's the best we've got so far, and it does provide seemingly reasonable results that also align with parallax measurements when parallax is within the usable range.