I think you're asking about intensity in the node manager? The plain Intensity (50) affects Color (blue) right above it, and Ambient Intensity (2) affects the Ambient Color (Red). So the blue lighting will be very bright, but the red lighting will be very dim. If you want extremely bright light, you can go up to something like 100 intensity.
Also, it helps a lot to raise omni lights further above the ground so the lighting spreads out more.