Color in is a phrase commonly used to describe the act of filling in an outline or design with colors. Color in can also be replaced by various synonyms such as fill, shade, tint, hue, pigment, paint, and dye. The words fill and shade can be used when referring to the action of completing a shape with solid colors. Tint, pigment, and dye are used to describe the color that is being applied to the design. Hue and paint can be used interchangeably to indicate a specific color or shade being added. Other synonyms for color in include colorize, cover, embellish, and highlight. These words all have different nuances and can be used to describe different techniques and styles of coloring in a design.