I can make a translucent background, but is there a way to add multiple translucent backgrounds to one element? Or do I need to multiply the values myself (and if I need to multiply the values myself, what formula would you suggest?) and set one background color?
You can set multiple background images…
Yes, with CSS3
Using CSS3
gradientcalls to make “non-gradient” solid colors will give you multiple background colors with transparency capability. Here’s two solid colors at 50% transparency overlaid (see a fiddle):