What exactly is colored sound?

In all the studios I’ve been recorded in, the engineers have mics they have come to prefer for specific applications. A lot of them like the Shure SM57, for instance---a PA vocal mic, for snare drum. The mic has a presence peak deliberately engineered into the mic’s frequency response, to make vocals coming through a PA more audible. Used as a recording mic, it adds the same presence region boost to snare drums, making them "pop" and "cut" in a mix better than does a mic with a flatter frequency response. Those engineers are not in the least concerned with capturing the inherent, true timbre of the drum, but rather to get a "good" snare sound, one that will suit the sound he is after in the entire mix.

I hear you loud and clear on that one- I've run into the same thing myself. With such recordings the idea of reproducing it in an uncolored way gets pretty weak...

If you actually had a copy of an original master tape, for example, and you played it on two different systems, lets say they are extreme high end, I bet that master tape would sound different on each to some degree even if you used the same reel to reel device.  So, unless you were present at the actual recording and heard it with your own ears, would you really know how it sounded?

 I guess that the only thing I could think of is that I want a trombone to sound like a trombone, a piano to sound like a piano and so on.  I cannot say I have heard systems that a trombone sounds like a trumpet lets say.  Whether in a hall that sounds warm or neutral, well I guess if we want to hear it in a warm hall, we may decide to tweek our systems to that way of listening and so on.

I have master tapes, and have encountered colorations due to playback. I actually made two master tapes of one project, as we wanted a backup. The backup machine was solid state. Starting right there, we noticed colorations simply on account of the machines used- the tube master sounded best on the tube machine in playback, sounded better than the solid state master while played back on the solid state machine, and the solid state master sounded best played back on the tube machine. So there is the initial colorations that the recording gear imposes...

Then there are the room, speakers and amplification, all which impose some sort of tonal coloration (more or less bass, more or less highs and so on).

Its impossible to know what is right unless you were there to hear how the actual performance sounded.

Colorations occur due to:

1) the room in which playback occurs
2) frequency response errors which all loudspeakers have
3) incorrect interactions between amp and speaker which cause frequency response errors
4) distortion, which is found in all things electronic

It turns out that the ear is less sensitive to certain colorations and a lot more sensitive to others. For example the ear is not particularly sensitive to the 2nd harmonic (which is responsible for the coloration of 'warmth', often found in tube equipment) but is extremely sensitive (moreso than most test equipment) to the 7th (which is part of what causes harshness and a metallic quality and is why solid state has the coloration of 'bright' and 'hard' and the like).

Frequency response errors are also obvious colorations with multiple causes!

But its much more complex than that- the ear has tipping points where it will favor distortion over actual FR errors. Brightness in solid state is one example of that.

Digital and analog recording processes both have colorations associated with distortion and bandwidth, although in the digital world, the word 'aliasing' is used because digital guys don't like to admit that digital makes distortion (my 2 cents on that....).

Microphones also have colorations- as a recording engineer, I love my Neumann U67s which turn out fantastic results, but I'll be the first to concede that they aren't perfect by any means!

@tzh21y with so many sources and causes, it might be helpful to put this in a context as the topic is a bit broad. Did you have a specific area of interest?