Tone ColorTone color or timbre of a sound is determined by the relative strengths, presence, and absence of the different harmonics and frequencies that a sound is composed of. On the guitar, if we emphasize the higher frequencies, a note sounds brighter. If we emphasize the mid-range and lower frequencies, it sounds darker. The manner in which you pluck a string determines which frequencies are amplified and which frequencies are diminished.

Simpler Definition:  A brighter color tone can be played closer to the bridge while a darker color tone can be played over the sound hole.

 

Video Explanations:

Video: What is Tone Color? (Timbre)

Video: What are Color Tones and how to use them

 

Written Articles:

Article: Tone Color and The Classical Guitar

 

Fifty Favorite Effect Pedals for Sale:

ClearancePedals.com