These three spin controls define the specular color of the material. Setting all three controls to 0 would give a black color and setting all three to 255 would give a white color. The RGB values can also be set using the Windows Color palette control by pressing the Pick button beside the controls.
The specular portion of a material describes what the material looks like in the areas of highlights or specular reflections. This is the area where a directional light bounces directly to the viewer’s location. We most readily identify specular areas by bright white spots on an object. The size and strength of the specular reflection area is controlled by the shininess of the material. You will need to change the shininess setting to get the specular effect to show up (esp. in the 3D Viewer).