The G major blues scale has 6 notes: G – A – B♭ – B – D – E. The major blues scale is the major pentatonic plus the ♭3. Sliding from the ♭3 up to the major 3rd is the signature sound of country and Chicago blues players; it brightens a blues without losing its edge.
Compared with the G major scale it has ♭3 (B♭ instead of B).
The explorer above is set to G major blues: the whole neck is mapped, and you can zoom into any of its 6 positions, change the labels to degrees or fingers, and hear it up, down and in patterns.