I ran into the same problem when using mix-blend-mode
in Google Chrome on a computer that has a DCI-P3 color gamut.
The reason that it happens has to do with color spaces. Blend mode calculations in some browsers are done in the display’s color space, which may not be sRGB, but CSS color declarations are in sRGB (unless specified otherwise).
A max-saturated CSS color such as #ff0000
is not maximally saturated in a larger color space like DCI-P3. colorjs.io’s converter shows that the reddest red rgb(srgb 255 0 0)
in sRGB is equivalent to a partially saturated red rgb(p3 235.052, 61.663, 46.740)
in P3.
On a P3 screen, multiplying magenta, cyan and yellow produces a result of multiplying these colors that’re partially saturated, and that doesn’t make black.
This article explains how that works.
Image in the article:

Read More : https://danielcwilson.com/blog/2020/03/blend-modes-in-spaaaace