Tradition of chips
Chips are used at casinos for several reasons. They are more convenient to use than currency. Because of their uniform size, stacking of chips is easy which makes the counting process also effortless. Chips instead of different currencies also make counterfeiting difficult and thus, make the job of verifying, by casino officials, trouble free.
Traditionally, colored chips used to be in red, white, blue, green and black but now they are available in many colors like orange, pink, yellow. Normally, less traditional colors are used for higher denominations like 500$, 1000$ and 5000$. Every casino has a distinct set of chips to distinguish them from one another. Most casinos do not accept chips of other casinos, except a few casinos in Las Vegas.