This is one form of the blues scale. You can move the form up and down the neck depending on what key you are playing.
For the major blues scale, the roots are: 6th string-4th fret, 3rd string-1st fret, 1st string-4th fret. For the minor blues scale, the roots are: 6th string-1st fret, 4th string-3rd fret, 1st string-1st fret.
The roots are in red. And the blues notes are in green.