The orange color represents the right hand and the blue represents music in the left hand.
The plot is showing that the form of the music is A B A C A. The A sections are highlighted in green in this image of the score:
The yellow highlighting is the music represented by the tall skinny arc, where the intro returns near the end of the piece. The red highlighted segment is not shown in the plot because it is showing exact-pitch matching. If you select relative-pitch from the homepage options, the red section would also link to the yellow section.
The slider underneath the arc diagram controls the minimum length of the match, which you can use to filter out small inconsequential matches as desired.
If you want to try the interface with this particular piece, you can download data from humdrum extras with the command:
humcat h://chopin/mazurkas/mazurka24-2.krn > mazurka24-2.krn
Or you can go to VHV via this link:
http://verovio.humdrum.org/?file=chopin/mazurkas/mazurka24-2.krn
and then type "alt-s" to save the file to your Downloads folder.