Probably the best way to test if you are doing it right is to compare to an optical blend. Say you blend red and green, such as by having a red ( rgb(255,0,0)

Probably the best way to test if you are doing it right is to compare to an optical blend. Say you blend red and green, such as by having a red ( rgb(255,0,0) ) div, and putting a div that is green with 50% transparency over it ( rgba(0,255,0,.5) ). Now, make a checkerboard pattern of red and green divs. Look at it from far away enough that it appears as a solid color. (easier if you make each div occupy one pixel, while trying to avoid any antialiasing) You could also use something like frosted glass to blur it. Do they appear the same color? I would not expect it to appear as a bright yellow, but a rather dark yellow. (but not so dark as it appears brown)