More questions about the Belt of Venus

I watched the Belt of Venus for some time at sunset. It is finally beginning to sink in that these are not clouds on the horizon. The sky looks blue during the day because oxygen molecules scatter the blue wavelengths back in our direction. The Belt of Venus is the pink band between the lower grey shadow of the Earth and the blue sky above which is still fully lit by the Sun. Accounts say that it is pink because of back scattering of red light from the Sun. So why isn't red light scattered back all the time? Is it because we are low in the atmosphere at this time and dust is now important? That's what I'm struggling with. Why isn't there any blue left if it is still being lit by the Sun? I've looked at a lot of articles and not had any definitive sense. They say the Band is between 10 and 20 degrees. My fingers would roughly agree. My next source for research will be https://en.wikipedia.org/wiki/Absorption_band since the Chappuis Effect was mentioned in one forum as contributing to the grey colour below the band. This was being disputed but at least gives me something to go on.