Probably more important for Blues than the major bar chord is the root 6 bar chord 7th. It can be thought of as a variation on the root 6 major bar chord shape. The only difference is that the little finger is placed one fret further up the neck on the second string. Like the major bar chord, the shape remains the same regardless of the position on the fretboard.
Practice changing between the major bar chord and the 7th bar chord, then try this 12 bar Blues which makes use of both.