Use the color to control the light’s brightness. For instance:

dlight.setColor( VBase4(  2.0, 2.0, 2.0, 2.0 ) ) 

This makes a light twice as bright as one that is just (1, 1, 1, 1). But note that when you exceed 1.0 like this, you’re in danger of oversaturating the colors on the models.

Lighting in a 3-D world is counterintuitive. Turning on lighting will always make everything in the scene darker than if you weren’t using lighting at all. This is because when you don’t use lighting, it is treated as if you had an ambient light of (1, 1, 1, 1) on everything–that is, it is as if everything were fully lit. As soon as you enable lighting, some parts of your model become less than fully lit.

If you want lighting to look bright, you will have to paint your models with this in mind.