Well. I suspect the difference is euphonic by itself is just an adjective. If
you attach it to a noun such as coloration then you have something specific. A
euphonic coloration is a deviation from accuracy by the fact that it is a
coloration. In the end all playback is colored. There is no such thing as
perfect accuracy in audio playback. So the question I think worth asking is;
when a euphonic coloration makes the end result seem to have more of the
intrinsic beauty of live music that is inevitably lost in most playback what is
wrong with that?