There are several different techniques we use to help distinguish between different types of polyp: (i) by pushing a button on the camera to change the colour of the picture (ii) to spray the surface of the polyp with special dyes to highlight the surface of the polyp. These dyes are harmless and temporary, and are also commonly used as a food colouring. However you may notice that the dye may temporarily change the colour of your stool (motion) to a blue/green colour after the procedure.