White, as the eye sees it, is the color with the least amount of pigment. So what looked like a white painted wall might be pink, or blue, or beige when you bring in a set of curtains with even less pigment then the paint used on the wall. The eye in conjunction with the brain defines white as a comparison with surrounding colors and ambient light. I recall a Color Theory class where we had to create a white on white scene using torn scraps of Pantone papers. It was both revealing as well as fun!
There are two ways to make white. One is by mixing of all colors of light (red, green, blue). The other is by removing pigment (cyan, magenta, yellow). (Although to produce most white paints, the manufacturers use mostly minerals that, when ground up, seem whitish. Zinc oxide is one example.)
For glass beads, whiteness depends on finish as well as the white pigment used to color the glass. The angle of incident light (light hitting a surface) also plays a role, but it is more transient. For the whitest seed beads, I prefer a shiny luster – the shinier the better! Matte beads tend to seem kind of greyish to me.
If you’ve never paid attention to the variety of white, try it now. And tell me what you have discovered for yourself in the comments below.