I should have clarified better: “Roon code” is the critical thing… Whether DSP volume is done by the Core with headroom adjustment or it’s done in the Roon Bridge or the device’s RAAT SDK, it’s all the same code.
I was one of the 2 people that designed/wrote this code 
Anyway:
The reason you are seeing signal path lights different is a tricky thing for us to display, but it’s just a display concern.
The purple glowy light means “bit-perfect”. I don’t think there is any misunderstanding here, but this would be the Roon gold-standard.
The blue glowy light generally means “good” but not “bit-perfect”. This would be the same as the non-glowy greenish light, but we use this light to imply that you meant to do this as an improvement, instead of as a side effect to lose bit-perfectness. The SQ may be even better than “bit-perfect”, but that’s for your ears to judge.
DSP Volume and Headroom both are not bit-perfect, so they should both be green. However, we clump headroom adjustment in with the rest of DSP because clearly it will make the audio not-bitperfect, but you knew that and are still using it to enhance the audio.
You are reading too much about what the light says about the quality.
All that said, the weirdest thing you’ve said is this:
I’m not sure why you say that, but that is EXACTLY where you want the attenuation. Everything else is an approximation of trying to do it in the analog stages… this is the place you get it with the best resolution (near infinite resolution!)