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Colour STEM Experiments

Hands-on science activities that help children explore mixing, absorption, and light. Perfect for EYFS, KS1, and curious KS2 learners.

Last reviewed on 30 April 2026.

STEM Science Investigation Vocabulary

Safety reminders

  • Supervise water experiments at all times.
  • Use aprons to protect clothing.
  • Encourage gentle handling of glass jars.

Classic colour experiments

Walking Water Rainbow

Fill six cups with red, yellow, and blue water, leaving gaps. Fold paper towels into bridges and watch colours walk and mix into secondary colours.

Sweet Science Rainbow

Arrange Skittles or M&Ms in a circle on a plate. Add warm water and watch the sugar dissolve to make a colour wheel.

Colour Chromatography

Draw a black line with felt-tip pens on coffee filters. Dip into water to reveal the hidden rainbow of pigments.

Light Spectrum Prism

Shine a torch through a glass of water to cast a rainbow on a wall. Compare the spectrum colours with paint samples.

Lesson structure

Start with a prediction prompt and model key vocabulary. Encourage children to draw what they see, then discuss why the colours changed.

  • Prediction: What colours will we make?
  • Observation: What is happening slowly?
  • Conclusion: Why did the colour move or mix?

STEM vocabulary bank

absorb, dissolve, pigment, mix, spectrum, transparent, opaque, gradient

Encourage children to use these words in full sentences for extra communication and language development.

Setting up a colour science table

A dedicated colour science table works for any of the experiments on this page. It keeps materials in one place, signals to children that this is investigation time rather than craft time, and makes tidy-up faster.

Surface

Cover with a wipe-clean tablecloth. Tape an A3 sheet to the wall behind for children to record what they notice.

Equipment

Clear cups, jugs, paper towels, food colouring, water, pipettes, coffee filters, felt-tip pens. Keep glass jars for older groups only.

What children are actually learning

Each experiment looks like one trick, but it carries several scientific ideas underneath. Naming those ideas — even briefly — helps children build a richer picture of why colour behaves the way it does.

  • Walking water. Capillary action: water travels through tiny gaps in the paper towel. Mixing two primary colours makes a secondary colour.
  • Skittles rainbow. Dissolving and diffusion: sugar coatings dissolve, the dye spreads through the water, and the colours stay separate because the water isn't moving.
  • Chromatography. Pigments: a "black" felt-tip is often made from several pigments mixed together. Water carries them up the paper at different speeds.
  • Light spectrum. Refraction: water bends light, splitting white light into the colours of the rainbow.

Common mistakes to avoid

  • Cups too far apart for walking water — the towel dries before the water travels.
  • Cold water with Skittles — warm water dissolves sugar much faster.
  • Permanent markers for chromatography — water-based felt-tips work; permanent pens won't separate.
  • Bright room lights for the prism — try a darker corner with one strong torch beam.

Differentiating the same experiment

Each of the experiments above can stretch from EYFS up to upper KS2 by changing the question, not the materials. Walking water for a Reception class is "what happens when red and yellow meet?". The same setup for Year 5 becomes "predict how long it takes the water to travel a longer paper-towel bridge, then test it".

For older children, layer in fair testing. Vary one thing — the length of the paper towel, the temperature of the water, the amount of food colouring — and keep the rest the same. Use the colour-by-fractions sheet as a follow-up that brings maths into the recording stage.

For curriculum links and a structured weekly plan, pair these experiments with the Early Years Colour Hub for younger groups, or the colour theory guide for older children moving from primary mixing into more nuanced colour relationships.