The cast glow can indeed be adjusted to change the relativity.  There are the atmosphere settings on the light and the actual atmosphere itself.  As I experimented I could see the ratio change as I tried different settings.  I did not do it enough to recall what yielded the proper balance, but I am sure it can be done.  The Attenuation setting on the Edge Blend has a big effect on the balance of the 2 colors added to the light.

 

I also narrowed the spotlight and it became a tight beam.

Atmosphere also has a Volume Noise which has major effect on this.