Pool is an indoor version of an old,old game played outside on green grass.Blue. It goes with most chalk. Why a lot of cloth was green, and most chalk was blue is one of the most mind-bending dichotomies of pool ever.
But, it is an obscure sport.
When people wanted to play indoors the forerunner to modern pool tables was born.
The green cloth was like the green grass they played on.
To keep the balls from falling off the table they added "banks" hence the reason we bank a ball.