All the coloring people are talking about the Octatrack has very little to do with the converters, it’s more the built-in effects and gain staging affecting things. Even a fully open filter (which is default on a track) will color the sound slightly.
The converters are fine, I’ve measured them quite a bit and they are pretty much on par with an RME Fireface. 
Maybe it would be more interesting to hear how different effect blocks affect the sound even on subtle settings.