Web-Safe Colors:
There are 216 to choose from. But they still don't look consistent from computer to computer, but they should be close.
Some monitors only display 8 bit color and are limited to 256 colors. 40 are used by system software and browsers, so we are left with 216.
-24
bit monitors can display just about anything. 35%
of people have these.
-16 bit monitors can display more than 8 bit. 55%
of people have these.
-8 bit monitors display 256 colors. 10%
of people have.
From Photoshop you can see all the possible web-safe colors in the swatches panel.
1. Open an image in Photoshop.
2. Choose Image>Mode>RGB if it is not already an RGB image
3. Choose Image>Mode>Indexed Color
4. In the Indexed Color dialog box, choose Web from the Palette pull-down menu.
5. Click ok.