How do you add color?

     Replace resistors with carbon-comps and caps with paper-in-oil, as much as possible.

           If using tube gear; pick NOS valves, manufactured in Britain.

          Always worked for the few customers of mine, that were so inclined.

Only analog source and tube equipment can get things done right. If you are lucky.

Don't expect much from the rest, save your funds.

The problem is not the lack or the excess of colors...

It is only a symptom or a manifestation of unbalanced components synergy or the presence of a too harsh and bright component or of a too warm one...

The debate between colors and neutral is a red herring from the real problem which is synergy between components and acoustic embeddings...Most of the time it is reducible to these three factors : badly designed harsh or too warm component instead of more neutral component , synergy between more colored and less colored components and the right acoustics embeddings of them all...

Then que question to ask is not how to add color to a liveless harsh and fatiguing or too clinical system but how to create a balance and a synergy between the components/room...

We cannot and should not add color to a system , instead we must create a better synergy and balance between each components using electrical, mechanical and acoustical embeddings controls to the necessary synergy between dac and amp and speakers .....

To answer rightfully to a question implied that the question must be ask in the right way...

And remember that as much as upgrading a "defective" component is not the solution to the problem of balance between component by itself, (for example buying tubes components),  nor a solution for their optimal workings condition ; embeddings controls are the solution after the right created synergy is reach... And this is true with or without tube components or with or without analog or digital components... These debates between tubes and S.S. are BESIDE  the problem...And people often present upgrade or purchase as a solution, which is not and cannot be  by itself THE COMPLETE SOLUTION...

Oh, almost forgot.  Mundorf Supremes, used in B&W and Magico, are very colorful, almost splashy. 

An expensive but effective way to add color, IMHO.  Too much for me! :)

I think that speakers or electronics that portray timbre and texture well are perceived by the mind as "colorful."