Color mixing for kids: what paint really does

What kids learn: mixing colours

Yellow and blue make green, on the screen too

In Professor Oops paint mixes like real paint, not like the light of a screen: yellow and blue make green, red and yellow make orange, and everything stirred together turns brown. Children find it out by painting, and you can check it with real paint.

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Ages 4+
Free in the game
A real-paint version for home

Painted illustration of the painter brushing a rainbow watercolour that bleeds into wet paper, with crayons, markers, a paint box and a child's rainbow drawing.

Quick facts

Age: 4 to 10
What they find out: Which colours make which, and why mixes get darker
In the game: Craft tab and the Paint board, all free
For real: Poster paint, a paper plate, about 20 minutes
Mess: Medium (it's paint)
Adult needed: To set up, and to squeeze for the youngest

Green from yellow and blue, brown from everything: six mixes they discover

Nobody has to tell them. Put two colours together on the paint board or on wet paper and the result is right there. These are the mixes that come up first:

Yellow and blue make green

The first big surprise: neither paint is green, but together they are. More yellow gives a bright yellow-green, more blue a deep blue-green.

Red and yellow make orange

A warm, reddish orange. Add more yellow and it turns towards tangerine.

Red and blue make a dark purple

Darker and duller than most children expect. Real school paint does the same.

Everything together turns brown

Keep stirring in colours and the puddle heads for brown. Every paint you add takes away a bit more light.

Opposites make mud

Red and green, purple and yellow, orange and blue: each pair mixes to a dull brown or olive. Painters use that on purpose to tone a colour down.

White makes it paler, black darker

A little black goes a long way. And black in yellow gives an olive colour, not a darker yellow.

In Professor Oops: every way real paint mixes

The drawing tools are in the Craft tab. Each one mixes the way its real version does:

On the paint board. Tap Paint board by the lower corner of the sheet: a wooden palette with ten Paint tubes (white and black included) and a Palette knife. Squeeze two colours, drag the knife or the brush through them, and watch the green, orange or brown appear. Dip the Paint brush in the mix and paint with it.
Wet paint into wet paint. Brush into paint that is still wet and the colours blend. The brush picks up a little of what it ran through, so the next stroke starts a bit muddy and cleans up as you go, just like a real brush.
Watercolour and marker, layer on layer. They are see-through: yellow over dried blue turns green without any stirring. Two wet watercolours that touch run into each other and blend where they meet.
Crayon, dark over light. Blue crayon over yellow turns green. Yellow over blue hardly shows, as with real crayons.
Paint covers, watercolour doesn't. Thick paint hides the paper and the lines underneath; watercolour lets them shine through.

All of it is free, the paint board too.

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Painted illustration of the painter sprinkling glitter on a glue star, beside salt on a glue line soaking up blue paint, stickers, ink droppers, a stencil and tape.

Painted illustration of paper strips and a coffee filter in glasses of water, where black marker dots have spread into blue, pink and yellow bands, watched by the painter.

Why yellow and blue make green: paint takes light away

Paint gets its colour by swallowing light. Yellow paint swallows the blue light, and blue paint swallows the red and the yellow. Mix them, and green is about the only light that's left to bounce back to your eyes.

For grown-ups. This is subtractive mixing: each pigment absorbs part of the light, so every colour you add takes more away, which is why mixes get darker and end in brown. A screen works the other way round. It adds coloured light: red and green light together look yellow. So a drawing app that simply averaged the screen colours of yellow and blue would give a greyish mush. Professor Oops instead works out how much of the red, green and blue light each paint absorbs, and mixes those amounts, weighted by how much of each paint there is. That's why its blue and yellow make green.

Want to see the screen side? Look at a white patch of a screen through a strong magnifying glass: on many screens you can make out tiny red, green and blue lights. And black marker ink turns out to be a mix too: paper chromatography splits it into blue, pink and yellow.

Paper chromatography

Where the game keeps it simpler than real paint

Just like real paint

Yellow and blue make green, not grey
More colours make darker mixes, and in the end brown
Opposite colours dull each other down
A little black changes a lot
See-through layers mix without stirring; thick paint covers
A dirty brush carries colour into the next stroke

Simpler than real paint

White is weaker. Real white paint also scatters light, so a little of it makes a colour pale fast. In the game you need more white to turn red into pink.
One blue is one blue. Real blues (and yellows) differ, and give different greens. The game has one of each, so its green always comes out the same.
Dry paint blends a little. Painting over dried paint in the game mixes into it for the first strokes; real dry paint takes a clean new coat.
It's still a screen. The result is shown with light, so a colour can look a little different from the same mix on paper.

For real

Try it with real paint

You need

Washable poster paint (tempera) in red, yellow, blue, white and black
A paper plate or an old lid as a palette
A brush and two jars of water: one to rinse, one kept clean
Thick paper, and a pencil to write on it
If you have them: a watercolour set and some crayons

A mixing chart in seven steps

Guess first
Ask: what will yellow and blue make? And red and blue? Write the guesses on the paper before any paint comes out.
Mix two at a time
A blob of yellow on the plate, a little blue beside it, stir. Paint a patch on the paper and write underneath what went in. Then red and yellow, then red and blue.
Add the dark one bit by bit
Start with the light colour and add the dark one a dot at a time. A dot of blue turns a lot of yellow green; it takes a lot of yellow to change blue.
Paler and darker
Add white to one colour and black to another. Then try a drop of black in yellow. Is it what you guessed?
Stir them all
A bit of every colour in one puddle, stirred. What colour is it? Try it again another day: brown, every time.
Mix without stirring
Paint a yellow watercolour stripe, let it dry, then paint a blue one across it. Green where they cross. With crayons: blue over yellow, then yellow over blue.
Compare with the game
Make the same mixes on the paint board in Professor Oops. Which came out the same, and which different?

Predict before you mix

Can you mix yellow?

Try any colours you like. Can any mix make yellow, or a yellow brighter than the one in the pot?

Which purple is brighter?

Red and blue, or pink and blue? Guess first, then mix both.

Order matters?

Is a yellow layer over blue the same as a blue layer over yellow? With watercolour, and with crayon?

How many browns?

Red and green, purple and yellow, orange and blue: do they all make the same brown?

For teachers

In class: a mixing chart, on the whiteboard and on paper

Colour mixing fits KS1 and KS2 art and design (techniques in using colour). The idea that we see colours because light bounces off things comes back in the KS2 Year 3 science topic on light. Let the class predict each mix, show it on the paint board on the whiteboard, then make the chart for real in pairs.

Ideas for teachers On the whiteboard

Questions parents ask

Which colours make green?

Yellow and blue. More yellow gives a bright yellow-green, more blue a deep blue-green. It works the same way in Professor Oops.

Why does my child's painting always turn brown?

Every colour stirred in takes away more light, so lots of colours together end up brown. Mixing two at a time and rinsing the brush in between keeps the colours clean.

What are the primary colours?

At school: red, yellow and blue. Printers use cyan, magenta and yellow, which mix to cleaner colours. Screens use red, green and blue light, which is a different kind of mixing: adding light instead of taking it away.

Does the app mix colours like real paint?

Yes: mixes behave like paint, not like screen light, so yellow and blue give green, not grey. It is simpler in a few places (white is weaker, there is only one blue), which this page lists.

From what age can children mix colours?

From about 4, with two colours at a time and a grown-up squeezing out the paint. Older children enjoy making a full chart and mixing a colour to match something they see.

Mix your first green

Squeeze yellow and blue on the paint board and stir. Then get the real paint out and see if it does the same.

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