Color in the East African cichlid is an inherited trait. Other traits that vary among these fish include teeth and jaw shape. The code for each one of these traits is found in genes located within the fish DNA.
A gene is a nucleotide sequence in DNA which encodes for some biological product with a function such as protein or RNA. In this case, gene codes for the proteins responsible for the colors, teeth and jaw shape. Sometimes only one gene controls a trait, but often is a trait controlled by multiple genes that interact.