Which of the following are the primary colours of light?
- (a)Yellow, Red and Green
- (b)Blue, Red and Green
- (c)Violet, Red and Yellow
- (d)Indigo, Violet and Green
Correct — B, Blue, Red and Green. The primary colours of light are red, green and blue (RGB). They are called 'primary' because they cannot be produced by mixing other lights, yet mixing them in the right proportions can reproduce almost any colour, and all three together make white. This matches how the human eye works — it has three cone types most sensitive to red, green and blue.
- (a)Yellow, Red and Green — Yellow is not a primary — it is a secondary colour formed by adding red and green light, so this set mixes a secondary in with two primaries.
- (c)Violet, Red and Yellow — Neither violet nor yellow is an additive primary; red, green and blue are the primaries of light (red, blue and yellow are the primaries of paint/pigment, a different system).
- (d)Indigo, Violet and Green — Indigo and violet are spectral colours but not additive primaries; only green from this list is a true primary of light.
The primary colours of light are red, green and blue. In the additive system these three cannot be made from other lights but can be combined to create the full range of colours seen on screens; equal amounts of all three give white. This mirrors human colour vision, which relies on three cone types tuned roughly to red, green and blue wavelengths.
The common confusion is between the primaries of light (red, green, blue) and the primaries of pigment/paint (often given as red, blue, yellow, or in printing cyan, magenta, yellow). The question specifies light, so the answer must be RGB — any option containing yellow or violet as a 'primary' is a distractor.
- Primary colours of light: red, green and blue (RGB) — additive system.
- Equal red, green and blue light combine to give white.
- Yellow, cyan and magenta are secondary colours of light.
- The human eye has three cone types sensitive mainly to red, green and blue.
- Listing red, blue and yellow — those are pigment primaries, not light primaries.
- Treating yellow or violet as a primary colour of light.
Asked directly as 'the primary colours of light are …' or by contrasting light primaries with paint/pigment primaries.
No directly related past PYQ was found.
- practice — not a real PYQ
The secondary colours of light are
- (a)Red, Green, Blue
- (b)Yellow, Cyan, Magenta
- (c)Orange, Violet, Indigo
- (d)Black, White, Grey
Answer(b) Yellow, Cyan, Magenta — each formed by adding two of the RGB primaries.
- practice — not a real PYQ
Human colour vision is based on cone cells that are most sensitive to
- (a)red, green and blue light
- (b)yellow, cyan and magenta light
- (c)ultraviolet light
- (d)infrared light
Answer(a) red, green and blue light — the basis of trichromatic vision.