“Color change” or “Color up” refers to exchanging a large number of smaller denomination chips for fewer chips of higher denominations.
For example, if a player has accumulated many $1 chips and wants to exchange them for larger denominations, they can request a “color change” and receive higher denomination chips in exchange for their smaller chips.
This helps to reduce the amount of chips in play and makes it easier to manage large stacks. The excess chips are usually removed from play and taken out of circulation.