The Minor Chord (or Minor Triad because it only contains 3 notes) is probably the 2nd most common chord in all types of popular music.  Most people would agree that they sound sad.  As usual, there are 5 basic finger forms that we use to play these chords (the E-A-D-G-and C Forms) on the neck of the guitar.  These forms can all be used as Bar Chords (movable forms) that can be moved up and down the fretboard to play in all 12 keys.  The bright colored dots represent the most common finger configuration within each form, while the faded color dots represent other possible notes that might show up in different voicings, inversions and slash chords.  If you're unclear about how the color coding works on these charts, visit www.guitar-instruction-free-lessons-online.com/guitar-chords .  If you need more information about the music theory aspects of this and all other chords, check out Scotty's video home study program at http://www.absolutelyunderstandguitar.com/ .