# Colour notation

Colour notation refers to the method used by colour models to identify and store colour values in a form recognisable to both computers and humans.

• The RGB colour model uses both decimal and hexadecimal triplets for colour notation. So RGB decimal and hexadecimal triplets look like this:
• R=255, G=128, B=0 is the decimal notation for orange.
• #FF8000 is the hexadecimal notation for orange.
• The HSB colour model uses decimal triplets for colour notation. So an HSB decimal triplet looks like this:
• H=30.12, S=100, B=100 is the notation for orange.
• The CMYK colour model uses decimal quadruplets for colour notation. So a CMYK decimal quadruplet looks like this:
•  C=0, M=61.48, Y=100, K=0 is the notation for orange.

Summary

###### About RGB decimal and hexadecimal colour notation

RGB colour values are expressed as either:

• decimal triplets (eg. yellow = 255, 255, 0).
• hexadecimal triplets (eg. green = #00FF00).
• Computer software is usually programmed to recognise both decimal and hexadecimal forms of notation.
• In both cases the notation refers to the amount of red, green and blue used to produce any specific colour.

RGB decimal notation

• An RGB decimal triplet is made up of three decimal numbers each with a value between 0 and 255 and written with commas between. So red = 0 to 255, green = 0 to 255, blue = 0 to 255
• Look carefully at the following examples:
• Red = 255, 0, 0
• Yellow = 255, 255, 0
• Green = 0, 255, 0
• Cyan = 0, 255, 255
• Blue = 0, 0, 255
• Magenta = 255, 0, 255

• RGB hexadecimal notation starts with a # sign.
• An RGB hexadecimal triplet is made up of three two-digit numbers each with a value of between  00 and FF and written without spaces between. So red = 00 to FF, green = 00 to FF blue = 00 to FF.
• Whilst decimal numbers count in 10’s, hexadecimal numbers count in 16’s. So 0 to 9 followed by A to F.
• 00 to FF represents a sequence of 255 values.
• 0 to 15 appear as: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E and F
• 16 to 31 appear as: 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 1A, 1B, 1C, 1D, 1E and 1F
• 32 to 47 appear as: 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 2A, 2B, 2C, 2D, 2E and 2F
• 48 to 63 appear as: 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 3A, 3B, 3C, 3D, 3E and 3F
• etc.
• 240 to 255 appear as: F0, F1, F2, F3, F4, F5, F6, F7, F8, F9, FA, FB, FC, FD, FE and FF
• Look carefully at the following examples that show matching hex and decimal values:
• Red = #FF0000 = 255, 00, 00
• Yellow = #FFFF00 = 255, 255, 0
• Green = #00FF00 = 0, 255, 0
• Cyan = #00FFFF = 0, 255, 255
• Blue = #0000FF = 0, 0, 255
• Magenta = #FF00FF = 255, 0, 255