How to color individual polygons in a low poly model? So I have been working on this low poly project and have most of the modeling done. So, I have begun texturing and ran into a problem. I can't figure out how to color each individual polygon of my model. Here let me explain.

  

Notice how this image(that I found in a google search) has polygons in the model and it transition from blue to red and even in the blue and red the saturation and brightness changes to achieve a more natural look. Now I understand this effect can be achieved with lighting, but I'm doing a landscape so one solid color will not look good. I'm looking for natural variations in color and can't figure how to color them individually.
That looks like it was done using vertex colors.

Go into Vertex Paint mode and apply your colors.  Note that faces will blend colors in a gradient based on their vertices' colors.  

Then, in your Blender Render material, select the Vertex Color Paint option.