Display set values on colorbar

I am plotting weather reflectivity data using contourf. I have it contoured in intervals of 5 from 5 to 60. Typically (as we know) the colorbar shows graduated colors, for example, extending from 5 to 10, 10 to 15, and so on. However, I want it to only display the colors for the contours I have plotted. In other words, only the color that represents 5, only the color that represents 10, etc. Is this possible? How would I go about doing this?