Why does a blue ball look blue?

1white light

Here's a simple blue ball. Sunlight hits it, and sunlight is actually made of every color mixed together.

2paint absorbs

The paint on the ball's surface is a picky filter — it soaks up red, orange, yellow, and green light as heat.

3blue bounces off

But blue light bounces right off the surface, unabsorbed — that reflected blue light is what shoots into your eye.

4eye reads it

Your eye's cone cells fire strongest for that blue wavelength, and your brain reads that signal and simply calls it: blue.