#1
What do the blue markets indicate on here...

the empty black circles means open string right, the solid black ones mean you play that note..

but blue?

#2
On the 1st and 3rd they mark octaves. No idea what its about though.
Quote by fukyu1980
LOL ! muther fuker i was gonna say that LOL!
#3
in this case, they're the notes that make the blues scale what it is. the blues scale is just a minor scale, with the flat 5th added - the flat 5th is highlighted in blue anywhere it shows up.