Color Pallets

256 color

In the 256 color mode, each pixel has a value in the range 0-255.

SCREEN
-------------------------
|                       |
|                       |
|           ---         |
|           | 6|<-------------pixel with value 6
|           ---         |
|                       |
|                       |
-------------------------

This value for the pixel is then used as an index into the color pallet table.

   entry RGB entry
     0    - - -
     1    - - -
     2    - - -
     3    - - -
     4    - - -
     5    - - -
-->  6   25 255 0
     ...

The RGB values (24, 255, 0 for this example) are then used
to set the colors shown by the RGB guns.
Normally these tables are 24 bit, or 8 bits per color.  That
would make 25 be 25/255 percent of the intensity of red, 255 full on for 
blue and 0 off for green.