The blues scale is a hexatonic scale with minor pentatonic scale. But because blues notes (or blue notes) have a different form, there can be no one blues scale. As named in contemporary jazz theory, its use is based on the key and not the chord, unlike some chords in jazz.
The semitone differences for a blues scale are 3-2-1-1-3-2 for instance- C-Eb-F-F#-G-Bb-C
References
↑Ferguson, Jim (2000). All Blues Scale for Jazz Guitar, p.6. ISBN0786652136.
12Arnold, Bruce (2002). The Essentials: Chord Charts, Scales and Lead Patterns for Guitar, p.8. ISBN1890944947.
↑Harrison, Mark (2003). Blues Piano: Hal Leonard Keyboard Style Series, p.8. ISBN0634061690.
↑J. Bradford Robinson/Barry Kernfeld. "Blue Note", The New Grove Dictionary of Jazz, Second Edition, London (2002)