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How Colour Numbers Work

If the text in the charts below is impossibly small, here's a version with larger text.

If you'd like to check the colour cube at the same time, right click the following link and choose New Window. Colour Cube. Drag the edges of the colour cube window inwards so that it's smaller.

I like to imagine that there was once a scientist who had eight fingers on each hand. Why else would someone need a number system based not on ten, but on sixteen? That thought aside, the colour numbers use sixteen digits, and those digits are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, a, b, c, d, e and f.
I can't get my head around it, and neither need you, except to remember that, when we’re writing colour numbers, f is the highest digit.
Things are simplified a bit by a convention that suggests we use just 0, 3, 6, 9, c and f. If you’re a PSP person you'll want to experiment and make subtle changes, but these do give us a reasonable spectrum.

Because computer colours depend on light rather than pigment, the higher the number the lighter and brighter is the colour. Black is the lowest number—000000—and white is the highest—ffffff. Whatever the number, it must have a hash sign in front of it, so you write black as #000000 and white as #ffffff.
Each pair of digits—remember that the six letters a, b, c, d, e and f are digits too—represents one of the three primary computer colours. From the left then, that’s # red red green green blue blue.

 #ff0000  #00ff00  #0000ff

When you combine two colours, the results are sometimes different from those you’d get with paint pigments.

#ffff00 Red + Green = Yellow. #00ffff Green + Blue = Aqua. #ff00ff Red + Blue = Fuchsia.

To make the colours softer, you put a higher number into the unused colour or colours.
Where you have a 0, for instance, you could put a c.

 #ffcccc  #ccffcc  #ccccff
 #ffffcc  #ccffff  #ffccff

To make the colours darker, you put a lower number into the used colour or colours.
Instead of f you could put a 9.

 #990000  #009900  #000099
 #999900  #009999  #990099

Whenever you use the same number in each position you get black, a shade of grey, or white.

 #000000  #333333 #666666  #999999  #cccccc  #ffffff

For those into grey, let’s make some subtle changes.

#000000 #010101 #111111 #121212 #222222 #232323 #333333 #343434
#444444 #454545 #555555 #565656 #666666 #676767 #777777 #787878
#888888 #898989 #999999 #9a9a9a #aaaaaa #ababab #bbbbbb #bcbcbc
#cccccc #cdcdcd #dddddd #dedede #eeeeee #efefef #ffffff  

For the sake of completeness, I should say that some colours can be written by their ordinary name. Those guaranteed to work (almost always) are aqua, black, blue, fuchsia, gray (note spelling), green, lime, maroon, navy, olive, purple, red, silver, teal, white and yellow

If you want to print this page as a reference, you'll need to go to Tools > Internet Options, click on the Advanced tab, scroll down to Printing and put a tick beside Print Background Colors and Pictures. Usually it's best not to have this option ticked, but in this case the background colours are part of the story.Do be sure to go back and remove the tick once you've printed this.

Questions or comments? I’d love to hear from you. My email address is here.

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