Phong shading required interpolation of the surface normals and surface locations across the polygons, so that any polygon would be shaded according to its angular orientation.
For all types of lighting the contribution of the light source to the color was calculated for every channel and then clipped to [0,1] range.
Resultant color was a simple combination of object color and the light source color:
Required Image 1, with the light source from the view point:
Required Image 2, with the light source on its right: