The color property in the dcvColor member of the D3DLIGHT2 structure is an RGBA color that defines the color of light that a light object emits. The most common color is white (R:1.0 G:1.0 B:1.0), but you can create colors as needed to achieve the desired effect. For example, you could use red light for a fireplace, or you could use green light for a traffic signal set to "Go."
Generally, you set the light color components to values between 0.0 and 1.0, inclusive, but this isn't a requirement. For example, you might set all the components to 2.0, creating a light that was "brighter than white." This type of setting can be especially useful when you use attenuation settings other than constant.
Note that although Direct3D uses RGBA values for lights, the alpha color component is not used. For more information, see Color Values for Lights and Materials.