Colour Mixer — Light & Pigment
Shine red, green and blue lights together or mix cyan, magenta and yellow inks, and watch the overlapping circles show why red + green light makes yellow while cyan + yellow paint makes green.
Light and paint mix in opposite ways. Light mixing is additive: the primaries are red, green and blue, red plus green light makes yellow, and all three together make white. Paint mixing is subtractive: the primaries are cyan, magenta and yellow, cyan plus yellow paint makes green, and all three together make near-black.
Light sources
Turn up each coloured light (0 = off, 255 = full brightness).
The colour wheel of light
Tap a segment to load it. Opposite colours are complementary — together they make white light.
Light vs pigment — quick comparison
| Light (additive, RGB) | Pigment (subtractive, CMY) | |
|---|---|---|
| Primary colours | Red, green, blue | Cyan, magenta, yellow |
| Start with | Darkness (black) | White paper |
| Mix all three | White | Black (very dark) |
| Red + green | Yellow light | Muddy brown paint |
| How it works | Each light adds wavelengths | Each ink absorbs (subtracts) one primary of light |
| Used in | Phones, TVs, projectors, stage lights | Printers, paints, dyes, inks |
Guess the mix
10 questions on mixing light and paint, the prism and your eyes. Keys 1–4 answer, Enter goes next.
Why light and paint mix differently
Light colours add together to make brighter colours, while paints and inks take colours away. That is why the same “red + green” gives yellow on a screen but brown on paper.
Pick a mode
Light (RGB) for screens and torches, or Pigment (CMY) for paints and printer inks.
Move the sliders
Watch the three circles overlap — the overlaps show the secondary colours live.
Read the codes
Copy HEX, RGB, CMYK or HSL, see the nearest colour name and its complementary colour.
Guess the mix
Test yourself with a quick 10-question quiz and beat your best score.
Primary, secondary, tertiary
Light: primaries red, green, blue → secondaries yellow (R+G), cyan (G+B), magenta (R+B) → tertiaries such as orange (red + yellow).
Pigment: primaries cyan, magenta, yellow → secondaries red (M+Y), green (C+Y), blue (C+M).
In art class the traditional painter’s wheel uses red, yellow and blue (RYB) as primaries.
Cone cells in your eye
The retina has about 6 million cone cells of three types, most sensitive to red (long), green (medium) and blue (short) wavelengths. Rods work in dim light but cannot see colour.
Yellow light and a red + green mix excite the red and green cones in the same way — so your brain sees both as yellow.
The prism and the spectrum
Isaac Newton showed that a glass prism splits white light into seven colours — VIBGYOR. This is dispersion: violet bends the most and red the least.
A second, upside-down prism recombines the colours into white light. A rainbow is dispersion by raindrops.
Why a leaf looks green
An object’s colour is the light it reflects. A leaf absorbs most red and blue light and reflects green. In pure red light the same leaf looks almost black — there is no green light for it to reflect.
Colour Mixer (Light & Pigment) — your questions
What are the primary colours of light?
Red, green and blue. They are called primary because no mixture of other lights can produce them. Mixing two of them equally gives the secondary colours of light: red plus green makes yellow, green plus blue makes cyan, and red plus blue makes magenta. All three together make white light.
Why does red and green light make yellow but red and green paint make brown?
Light adds: each beam contributes its own wavelengths, so red plus green excites the red and green cones exactly as yellow light does, and your brain sees yellow. Paint subtracts: red paint absorbs most non-red light and green paint absorbs most non-green light, so between them almost everything is absorbed and you get a muddy brown.
What is the difference between additive and subtractive colour mixing?
Additive mixing starts with darkness and adds light, so the mixture gets brighter — it is used in phones, televisions, projectors and stage lights with the primaries red, green and blue. Subtractive mixing starts with white paper and each ink absorbs part of the light, so the mixture gets darker — used in printers, paints and dyes with cyan, magenta and yellow.
What are the seven colours of the rainbow?
Violet, indigo, blue, green, yellow, orange and red, remembered as VIBGYOR. Isaac Newton showed that a glass prism splits white light into this band of colours, a process called dispersion, because each colour bends by a different amount — violet bends the most and red the least. A rainbow is dispersion by raindrops.
Why does a leaf look green?
An object's colour is the light it reflects. Chlorophyll in a leaf absorbs most of the red and blue light falling on it and reflects green, so green light reaches your eyes. Shine pure red light on the same leaf and it looks almost black, because there is no green light for it to reflect.
What are complementary colours?
Two colours that combine to give white light are complementary — red and cyan, green and magenta, blue and yellow. On a colour wheel they sit directly opposite each other. In painting, complementary pairs placed side by side look especially vivid, which is why artists use them deliberately in posters and designs.
How do our eyes see colour?
The retina contains about 6 million cone cells of three types, most sensitive to long (red), medium (green) and short (blue) wavelengths. Your brain compares their signals to work out a colour. Rod cells are far more numerous and work in dim light, but they cannot tell colours apart — which is why everything looks grey at night.