Color image processing is very useful because color is a strong marker that also simplifies the recognition and extraction of objects from a scene and humans can distinguish thousands of shades of color and intensity compared to just around two dozen shades of grey. The processing of color images can be classified into two main areas as full-color and pseudo-colour. The images are first acquired with a full color sensor such as color TV camera, color scanner and second category has the question of assigning a color to a different monochrome intensity and intensity ranges. The aim of a color model is to promote color specification in a widely agreed way to some standard. A color model is a coordinate system specification and a subspace within that system where a single point represents each color. Some particular conversions can convert different color models to one another. This paper specify overview of different types of images, color models, their conversion and applications.