Computer Crayons

When you use crayons or paint on white paper, you're not adding colour - you're taking it away!

Drag these coloured balls below around. Try moving one ball onto another. How do the colours change? What happens when all three colours overlap?

 Yellow ,  cyan  (light blue) and  magenta  (purple) are the subtractive primary colours. The white background is a mixture of the additive primaries  red ,  green  and  blue .

Each subtractive primary removes just one of those colours; for example, yellow takes away all the blue, leaving just red and green. And your eye perceives a mixture of red and green as just one colour, yellow.

Can you figure out what colours magenta and cyan subtract? Try it out, then check the answer.

The colours you get by overlapping the balls in pairs are the additive primaries. That's because each subtractive primary takes away just one colour from the background. So two subtractive primaries let only red, or green, or blue get through.

This is the way paint and crayons mix. Try it with some crayons and a white piece of paper.

Did you know?

What you've seen here is not really happening! The only colours your computer can display are red, green and blue, so the SciZone simulates yellow by turning off all the blue pixels in the the ball. On the computer screen, the "yellow" ball isn't really yellow, it's a "no-blue-allowed" ball.