An RGB colour wheel provides a graphic representation of the RGB colour model.
A colour wheel is a diagram based on a circle divided into segments and can be used to explore the effect of mixing adjacent colours.
- RGB colour wheels have a minimum of three segments or spokes. These are filled with the additive primary colours red, green and blue .
- Starting with the three primary colours, an RGB colour wheel can demonstrate the effect of mixing adjacent segments to produce progressively subtle gradations of intermediate hues.
- An RGB colour wheel is particularly useful when trying to visually identify and specify:
- A particular RGB colour
- The relationship between different RGB colours
- Find the colour value (code) for an RGB colour.
- LED light sources producing very narrow bands of wavelengths can be used when demonstrating RGB colour wheels by projecting red, green and blue lights onto a neutrally coloured surface.
- The peak wavelength for selected lights might typically be red = 625 nanometres, green = 500 nm, blue = 440 nm.
About RGB colour and colour perception
- The human eye, and so human perception, is tuned to the visible spectrum and so to spectral colours between red and violet.
- RGB colour is a model used to reproduce colour in a way that matches human perception.
- An RGB colour wheel helps to simulate:
- The effect of projecting lights with wavelengths corresponding to the three primary colours, red, green and blue onto a neutral coloured surface.
- The additional colours produced by mixing adjacent pairs of colours such as adjacent primary, secondary, tertiary colours etc.
- Remember than the RGB is an additive colour model used when mixing light of different wavelengths. The CMYK subtractive colour model is often used when mixing paints, dyes and pigments.
About RGB secondary colours
- When pairs of primary RGB colours of equal intensity overlap they produce secondary colours:
- Red and green light sources overlap to produce yellow.
- Green and blue light sources overlap to produce cyan.
- Blue and red light sources overlap to produce magenta.
- Mixtures of pairs of secondary colours are called tertiary colours.
RGB colour wheels: adding intermediate colours
- Additional colours on an RGB colour wheel are always produced by overlapping equal intensities of adjacent pairs of colours.
- The range of colours that can be produced by an RGB colour wheel is limited only by the system of notation and the resolution of the device they are displayed on.
- The best way to calculate the correct code for an intermediate colour on a colour wheel is to work from a table. Examples of tables you can find here at lightcolourvision.org are shown below.
