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:
- 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
RGB colour wheels
- RGB colour wheels have a minimum of three segments or spokes. These are filled with the red, green and blue additive primary colours.
- Starting with the three primary colours red, green and blue, an RGB colour wheel can demonstrate the gradation of intermediate hues.
- An RGB colour wheel is particularly useful when trying to visually identify a specific RGB colour, the relationship between different RGB colours or to find the colour value (code) for an RGB colour.
- The bands of wavelengths corresponding with the observation of red, green and blue in a rainbow are typically:
- Red = between 620 – 750 nanometres.
- Green = between 495 – 570 nanometres
- Blue = between 450 – 495 nanometres
- LED light sources producing very narrow bands of wavelengths can be used when demonstrating RGB colour wheels by projecting red, green and blue LED’s onto a neutrally coloured surface.
- The peak wavelength for selected lights might typically be red = 625 nanometres, green = 500 nm, blue = 440 nm.
Secondary RGB 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.
Adding more intermediate colours
- Additional colours on an RGB colour wheel are produced by continuing to overlap 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.