The acoustic definition of " color" is related to the definition of timbre experience which can be understood and must be understood in psycho-acoustic by at least 5 physical acoustic criteria which are influenced by simultaneously the room speakers relation and the gear components characteristics and also by psychological evaluative perception ( the state of emotions and the individual music journey ) ...
It is a complex matter pertaining not just to gear design quality but also to physical room acoustics in specific relation to specfic gear system design and to the psycho-acoustic conditions linked to timbre experience and evaluation which imply subjectivity and neurology...
In a sense the question of the OP is a road to misunderstanding by underestimating the complexities of the timbre experience, with the implicit presupposition that the gear will be the main factor...
The better question will be : how do we improve timbre experience ?
For sure i could understand this question as a question not about fundamental acoustics but about the gear pieces...This is not wrong to ask this question about the synergy of gear pieces in one direction : warm, cold , neutral...My claim is that this question about gear colors is not meaningless no , but it is misleading question which stay on the problem surface ...