Hexadecimal Colours
Red, Green and Blue
Hexadecimal numbers are used on web pages to set colours.
The colour is defined by its mix of Red, Green and Blue, each of which can be in the range:
0 to 255 (in decimal) , or
00 to FF (in hexadecimal)
Because a colour can be made by mixing Red, Green and Blue. So
it is called the "RGB Colour System".
It is also called an "Additive" colour system, because it starts at
black, and then colour is added.
Colour Mixer
Try mixing your own colours to see how it works (or type values into the hexadecimal or
decimal boxes):
See Interactive Colour Wheel http://www.mathsisfun.com/numbers/color-wheelinteractive.html
Hexadecimals
Hexadecimal numbers are "natural" to computers, because computers store and handle
binary digits, and four binary digits make one hexadecimal digit (see Binary Digits):
Decimal:
Binary:
01 2 3
4
5
6
7
8
9
10
11
12
13
14
15
0 1 10 11 100 101 110 111 1000 1001 1010 1011 1100 1101 1110 1111
Hexadecimal: 0 1 2 3
4
5
6
7
8
9
A
B
C
D
E
F
Two Hexadecimal digits together (called a "byte") can make 16×16=256 different levels of
colour.
16 Million Colours
Because each of the three colours can have values from 0 to 255 (256 possible values), there
are:
256 × 256 × 256 = 2563 = 16,777,216 possible colour combinations
(and this is why you see claims of "16 Million Colours" on computer equipment)
Web Format
The format ("notation") used on web pages is #RRGGBB, where RR is how much Red (using
two hexadecimal digits), GG is how much Green, and BB how much Blue.
Example: a nice shade of blue is made up of:



64/255 Red,
48/255 Green
255/255 (i.e. full) Blue
So it is (64,48,255) in decimal, which is equal to (40,30,FF) in hexadecimal and would be
coded as #4030FF.
This may help you remember:
Roses are #FF0000
Violets are #0000FF
Just don't forget,
Grass is #00FF00, too
Some Common Colours
Colour
Decimal
Hexadecimal
(Red, Green, Blue) (#RRGGBB)
Black
(0, 0, 0)
#000000
White
(255, 255, 255)
#FFFFFF
Red
(255, 0, 0)
#FF0000
Green
(0, 255, 0)
#00FF00
Blue
(0, 0, 255)
#0000FF
Yellow
(255, 255, 0)
#FFFF00
Cyan
(0, 255, 255)
#00FFFF
Magenta (255, 0, 255)
#FF00FF
Try entering the hexadecimal code into the colour mixer above, and see what you get (you
can copy, then right-click the hexadecimal box, and select "paste").
I have also compiled a much longer list of Hexadecimal Colours and their Names.