From the excellent Poolguitarblog, many thanks and strongly recommended
go to: http://bit.ly/MXe0Ee
The blue square indicates a triad. In the part about the major 7 chord you can see the !, IV, an V are blue.
When you see the Cmaj7 as the IV chord in the scale of G, you can also use the triad of D.
The blues scales are orange. Scott uses them a lot as we know. I have a video on this blog where he talks about the blues scales starting on the II, III, and VI chord(tone).
The minor7 b5 arpeggio is indicated by a triangle.