Color values are indicated using their hexadecimal number for the combination of RGB values. The lowest number is 00 (black) and the highest # is FF (white). There are 16 million possible hex combinations in all. There are only 256 web safe combinations. This chart shows some colors resulting from different hex numbers.
In addition to using hex numbers to indicate color in web design, there are 16 color names that can be used in their place in accordance with the W3C HTML 4.0 standard. They are represented in the following chart. All other web colors should be indicated by their hexidecimal value.
For more helpful charts like these check out the Media Bakery Community page!