Color numbers

You can specify exactly what color you want by specifying the three primary colors:
bright Red, bright Lime Green, bright Blue
You give a two digit number for how much of each color you want
Each digit is one of the hexadecimal digits from 0 up through f:
0 1 2 3 4 5 6 7 8 9 a b c d e f
So for none specify 00 - for maximum specify ff
To specify the whole color number specify
    #   the number sign, followed by
    two digits for red, followed by
    two digits for lime, followed by
    two digits for blue
The samples show:
#ff0000   -   #   ff (max red)   00 (no lime)   00 (no blue)
#00ff00   -   #   00 (no red)   ff (max lime)   00 (no blue)
#0000ff   -   #   00 (no red)   00 (no lime)   ff (max blue)

Here are 16 colors, with their color numbers also shown.
You can specify colors by name or color number.

If you want a darker shade, use a smaller number
This sample shows shades of blue from bright down to black, and shades of yellow from bright down to black.

When I want a particular color, I may just use trial and error.
For example, I want a light blue color.
Start with blue #0000ff
To make it lighter, I need larger numbers to get closer to #ffffff white. I cannot make the blue any larger than ff, so try making the other colors lighter.
Try #c0c0ff
Too light. Try #a0a0ff
Perhaps. Try #b0b0ff
About right, but try a little more lime. Try #b0b8ff
Tip my screen up; look at it carefully; that looks OK.
Notice that I started with the main color I wanted, then added some of the other colors. Each color has two digits. Change the first of the two digits for each color first; they make most of the difference. Then make minor changes by changing the last of the two digits for each color.

There are some other ways to specify color, using percent, or only one hexadecimal digit for each color, or decimal numbers. The way we did it here with the number sign and 6 hexadecimal digits always works well.