Ambient color is a small constant (light) color that is multiplied to the final resulting pixel color, thus making it look like there is always some scattered light even if there isn’t any light source in the scene.
You can turn off Show light sources to hide light sources in the viewport.
|TIP: To prevent a light source from illuminating your scene, deactivate its visibility in the Object List.|
Enable Gamma correction to apply gamma correction to the final output color before displaying it to the monitor.
Press Compute shadows to update shadows cast from all visible light sources in the scene.