Websave colour palette
Every colour combination can be recalculated to a hexadecimal value and thus be used in the HTML file. The amount of possible colours with the 256 per R, G and B will give us a total of 256x256x256=17,777,216 combinations.
For the WWW a restricted number of colours is used. The reason for this is the fact that (the older) pc-systems only can show 256 colours at a time. The graphic cards did not handle more. Nowadays they can show millions of colours, so restriction in the number of used colours on a web page is not really needed. For reasons of minimizing file sizes (to decrease download time of the data) and to give all WWW-surfers the optimal image quality (not everyone has the most up-to-date equipment) a limited amount of colours is used.
When you want to be sure that all surfers see the colour in the same way as intended, a specific set of colours has to be used. This set contains 216 different predefined colours and is called the "Websave colour palette".

Indexed colours
For showing images on the Web we use 256 or fewer colours of the complete possible set: we make use of "indexed" colours. These colours have a linked colour palette, which is also referred to as a CLUT (Colour Look Up Table). Each colour in this table has a number. The image refers to the numbers used in that palette. The Websave colour palette consists of 216 colours and each user will see these colours as you choose them. When a user does not have a PC that supports millions of colours, and it happens that you made use of other colours than in the Websave colour palette, the "other" colours will be dithered. (A combination of colours from the Websave colour palette will be used to replace the original colour and this can look quite awful).

The complete Websave colour palette

The list of all 216 colour codes is too long to reproduce here . The hexadecimal numbers used are following: 00, 33, 66, 99, CC, FF. Each number corresponds to one of six intensity levels of R, G or B. The total number of colours produced is therefore 6 x 6 x 6 = 216.
In most graphic software packages this list is a standard part of the large choice of colour palettes available. Shown here are a few codes in each of the following ranges:
Bluish: #0000FF, #0033CC, #006699, #3399FF, #33CCFF
Greenish: #00FF00, #00CC33, #66FF00, #66FF99, #339900
Yellowish: #FFFFCC, #FFFF66, #FFFF00, #FFCC00, #CCFF33
Reddish: #FF0000, #FF3333, #FF6600, #FF3399, #990000
Purplish: #660066, #CC00CC, #663399, #CC33CC, #FF66FF

Action
Open the HTML file of "LovelyMaps" and add some colour to the background, text and table cells. Have a look at what colour does to a page ...