When laundry powder manufacturers want clothes to appear “whiter than white” they add a trace of blue dye. When hair dye manufacturers want hair to appear blacker than black they add a trace of blue dye. Blue is both a white intensifier and a black intensifier.
Which is actually a pretty good art tip
Very few things in nature are blue or blue-tinted.
Traces of yellow (opposite of blue) turns whites to off-whites and blacks to browns, (both colors quite common in our natural world).
So our brains interpret blue-tinted colors as “whiter than nature” and “blacker than nature”.
I guess this also explains why I feel like I’ve crossed halway into an alien dimension whenever there’s an ultraviolet light turned on