Classify image by histogram

Hi, I am new for Matlab. I need your help , How to write the code in Matlab.

If I have one histogram graph, for example <http://tinypic.com/view.php?pic=ka05tc&s=5>. I would like to classes pixeles by range of intensity distribution (0-255). The we fill pixeles in each range by different colours back into the image. If intensity number 0-50, I want these all pixel to be Red. If intensity number 51-100, I want these all pixel to be Green. If intensity number 101-150, I want these all pixel to be Blue. If intensity number 151-200, I want these all pixel to be Yellow. If intensity number 201-255, I want these all pixel to be pink.

The final image will consist of these 5 colours.

Many Thank Warin