Squash (sport)
The ball is made of rubber. It is hollow. When it is warm (due to being hit many times) it bounces more. Balls are marked with different coloured dots. They are made to bounce at different speeds depending on the colour of the dots. Balls with two yellow dots are slow, while balls with one yellow dot are a little bit faster. Balls with green or white dots are average. Balls with red or blue dots are fast.