These are the 216 colors which any web browser should be able to display without dithering and thus display more quickly and accurately. Thus, when creating graphics for the Internet, it's best to use these colors whenever possible.
Click on a color square, and its RGB hex code will appear in the box.
Each color value is 3 bytes -- one each for red, green and blue ("RGB") in that order. Each byte will be two hexadecimal ("hex") digits (0-F), but the only guaranteed non-dithering colors use the byte value combinations of 00, 33, 66, 99, CC and FF.
Examples: "#666666" (gray), "#FF9900" (orange) and "#6600CC" (blue-violet).