1. Colour CPSC 1030

2. Colour ● Models ● RGB ● CMY(K) ● HSB (or HSV) ● RYB ● Harmonies ● Monochrome ● Complementary ● Analogous ● Triadic

3. Colour Models ● a mathematical way of representing colours as numbers ● each colour is represented as a group of 3 (or 4 ) numbers ● each of the 3 (or 4) dimensions has some meaning in terms of the colour device (printer, monitor, etc) or some other useful measure

4. RGB Model ● additive model ● (R)ed, (G)reen, (B)lue ● used for light emitting devices (e.g. LCD monitors) ● seconday colours are cyan, magenta, and yellow ● also used for most raster file formats for the web (e.g. PNG, GIF, JPEG)

5. RGB Model

6. CMY(K) Model ● subtractive model ● (C)yan, (M)agenta, (Y)ellow, (K)ey (black) ● used for light reflecting devices (e.g. printers) ● secondary colours are red, green, and blue ● black is added as a fourth component because combining cyan, magenta, and yellow dyes often does not produce a satisfactory black; also a lot of printing involves black text

7. CMY(K) Model

8. HSV (HSB) Model ● (H)ue – angular measure of colour ● (S)aturation – how pure the colour is; white, black, all grays have no saturation; usually expressed as a percentage ● (V)alue (or (B)rightness) – for colours with 0 saturation, black has value of 0 and white has a value of 0% ● useful for colour selection

9. HSV Model

10. RYB Model ● subtractive model ● (R)ed, (Y)ellow, (B)lue ● historical/traditional colour model ● still extremely useful for selecting multiple colours that “work well together” (i.e. colour harmony)

11. RYB Colour Wheel ● three equally spaced primaries (red, yellow, blue) ● other colours are subtractive combinations of the primaries

12. Colour Harmony ● a set of colours that “work well together” ● frequently based on a formula for selecting hues from the RYB colour wheel ● additional colours are introduced by varying the saturation and brightness of the basic hues ● basic harmonies: monochrome, complementary, analogous, and triadic

13. Monochrome Harmony ● one hue, variations in saturation and brightness

14. Complementary Harmony ● two hues on opposites sides of the colour wheel

15. Triadic Harmony ● three equally spaced hues on the colour wheel

16. Analogous Harmony ● three adjacent hues on the colour wheel