You've seen each lamp by itself. Now use color to see how they work together:
Select Layer 1, and then press the Shift key while selecting Layers 2, 3, and 4.
Select the Spot_Key lamp, to the left of the camera in the Top view, with theRMB. In the Properties window header, select the Object Data button. It's the seventh button from the left. It has a light bulb on it.
In the Lamp subpanel, select the white Light Color button below the row of buttons that define the kind of lamp you are using. In the pop-up color wheel, set G 0.0000 and B 0.0000 so that the lamp is red.
Select the Spot_Fill lamp to the right of the camera with theRMB.
In the Lamp subpanel, select the white Light Color button. In the pop-up color wheel, set R 0.0000 and G 0.0000 so that the lamp is blue.
Select the Spot_Back lamp, opposite the camera, with theRMB.
In the Lamp subpanel, select the white Light Color button. In the pop-up color wheel, set R 0.0000 and B 0.0000...