"Anything that is not part of the original signal is noise or distortion. Now it seems that some audiophiles in some situations enjoy some added noise/distortion, so in those cases we could consider it euphoric coloration."
Speed, so in these terms, dither in a digital system would be considered noise/distortion. But, dither actually results in higher resolution (this is proven and accepted digital theory). Dither does not result in added coloration or euphonic distortion.
(some, I have not used them all) Synergistic products like the Powercell UEF, do result in increased resolution, the Powercell UEF does not add color, or something additional to the perception of music, it strips away problems which allows the listener to hear deeper into the noise floor. This result is indisputable, and anyone who tries will have the same result.
Just because you do not understand the mechanism by which it works, does not mean it does not work. I do not understand it either, but I am thinking it may work in a similar fashion to dither, or perhaps, it adds a noise component which is in the inverse to noise prevalent on AC power, resulting in some cancellation.
In any case, the Powercell UEF does result in increased resolution, this is not debatable, one can hear details which were not present without it, not added color, actual detail. This perception is not to subject to any bias, as the details were not there before, a bias cannot make previously unheard details audible.
I have no experience of Synergistic products adding a "color" (tonality shift). In terms of adding color, say a warm sounding tube amp, for example: this amp will add the same color to all music, it will make Aaron Copland (listening to now) warmer, and it will make Nine Inch Nails warmer. Synergistic products do not do this. Synergistic products do not create a tonal shift which effects all music the same way. Synergistic products give you more of what any music is offering, Nine Inch Nails gets edgier, more dynamic, and more spatially defined, etc.