Mrtennis, I tend to agree with you on your statement regarding manufacturers not wanting to admit to designing gear with a "coloration." The term coloration is fairly perjorative so it's avoided most of the time. I would agree that you are seeking a certain coloration in your system, which can be extremely pleasant.
However, I would disagree with your generalization (someone once said, "generalizations are generally wrong") that one brand sets could not obtain such coloration. I have used several sets which seem more colored relative to others. i.e. I would suggest that Jena Labs, Magnan Cables and Tara Labs have more of a colored, or particular tonal sound, than Harmonic Technology, WireWorld or Clarity Cable. This becomes apparent immediately upon hearing them in any system compared to the others.
How many entire sets of cables have you tested/compared in order to arrive at your conclusion? I can respect your experience if you have worked with five, seven or ten sets. But if you just tried one or two then you lack much experience in this matter. No amount of logic can replace experience with cables.
I do believe you an exception, as I don't think most audiophiles would willingly want less defintion/detail in their systems and to introduce a perceived coloration (I realize we are speaking generally here and cannot pin down the precise experience). I believe that is a major mistake in setting up audio systems. Now, of course it's "my opinion," and you are free to enjoy whatever kind of sound you want.
I believe, Mrtennis, that you are settling for less than you could have. I find that most audiophiles are content with sound that is far under the potential of the equipment and that cabling plays a huge role in that under-performing. No matter whether you wish for your coloration or not I believe there are cable brands which would do what you want better than a hodge-podge of cables while introducing no unwanted characteristics.
Now, I perfectly understand yours and Calloway's method of using a couple of different cables to adjust the system when a set of cables is too strident. I insist that it means you have the wrong set of cables for your taste! Simply put, if you don't love the sound of the system with the set of cables you have tried, sample a different set. Sure, you can adjust it with a couple of different ones, but you will also be influencing the positive characteristics you did enjoy about the set.
The bottom line is that mixed cables give no direction toward purposeful movement of an audiophile's rig toward the desired sound. It's a guessing game. If you guys knew what a particular cable brand sounded like you would be able to select it for the desired effect. Even if you did mix it you would know what the cable would do for the system. You cannot know that unless you have the native sound of the cable in your mind from using it as a single set.
In my second system at the office I happen to have a mixed set of cables, about 3/4 of WireWorld and a couple others. This is by necessity rather than choice; I put my money into the main rig in my listening room. If I were to put more money into it I would not use the mixed cables; this system is entirely for non-critical listening but for background music while I work.
I know fairly well what would happen if I put in one or two different brands of cables I'm familiar with, whether tonality would suffer, whether detail and definition would increase, whether a coloration would be introduced. Just throwing a new untested cable into the mix is a crap shoot. Too many audiophiles are doing so and are encouraged, even by reviewers, to do so. It's a great way to spin your wheels and get nowhere. :)