How else could it sound different? If one box that gives you ruler flat frequency response, and noise and distortion levels that are a couple orders of magnitude below where anyone could dream of hearing (a good SS design), and you compare it with another box and hear differences, the differences are either a product of bias/imagination, or 'coloration'. What do you think coloration is? It's a difference in frequency response, added noise or distortion.
I don't want to hear my gear. I just want the ability to hear the music I am playing however it was signed off, in the same way I won't load up my plate of food at a Michelin starred restaurant with salt and ketchup before I've even tasted it. I can always season to taste after, but you can't take out that baked in dirty.