Using hexadecimal color references

Generally speaking, the built in color names like red, green, puce and teal are not up to scratch in a real web situation. For a start, there’s no universally defined standard of what colour puce actually is. Is it a reddish brown, or more of a browny red? For most circumstances we need to define our colours more accurately using Hexadecimal colour notation, commonly called Hex codes.

Hexadecimal is base 16. Our everyday decimal notation uses base 10, so we count from 0 to 9, then start again at 10. There’s nothing special about base 10, We just happen to have 10 fingers so it makes finger counting easier.

The ancient Egyptians counted finger joints, so used base 12. To this very day, we still use their 12 hour clock.

Hexadecimal Decimal Equivalent

In Hex, we count from 0 to 15, then start again at 10. To represent the numbers from 10 to 15 we use the first six letters of the alphabet like so:

Decimal Hexadecimal
1 1
2 2
3 3
4 4
5 5
6 6
7 7
8 8
9 9
10 a
11 b
12 c
13 d
14 e
15 f
16 10
17 11
18 12
19 13
20 14
21 15
22 16
23 17
24 18
25 19
26 1a
27 1b
28 1c
29 1d
30 1e
31 1f
32 20

The reason we do it like this is because of the way information is stored in a computer. Basically, 16 is 2 to the power 4. This means that the numbers 0 to 15 can be represented completely by 4 binary digits with no wasted memory.

Computers use binary digits, and wasted memory is bad. That memory aint free ya know.

Colour values are always expressed using 3 hex numbers jammed together, one number for each primary colour: Red Green and Blue.

For example, if we wrote #f00 that would be red full, green off and blue off, making a nice fire engine red colour.

There are two ways to write a hex code, long form and short form. Long form is more accurate, short form is quicker to type. Short form uses a single hex digit for each colour component. Long form uses two, making it more accurate.

Some example Colours

Red Component Green component Blue Component Colour
0 0 0 Black
f f f White
8 8 8 Mid grey
0 f 0 Full green
f f 0 Full Yellow

To make an item full green, we might type:

<p style="color:#0f0">Some green text</style>

To make it pale blue we might add a little more red and yellow making it lighter like this:

<p style=”color:#99f”>This text is pale blue</p>

The same colour expressed in long notation would look like this:

<p style=”color:#9999ff”>This text is also pale blue</p>

Exercise - Pick some colours

  1. Enter the following document and wrap each line in p tags
  2. For each line, add styling to make it the correct colour.

Use this document:

This line is dark grey
This line is full red
This line is rosy pink
This line is dark blue
This line is mid green
This line is purple
This line is the colour of a brown paper bag.
This line is the colour of a stormy sea
This line is the colour of a streetlamp in the early evening.
Next Exercise: Entity references >>>
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