Blues Scale

The (Hexatonic)/Blues Scale is a Minor Pentatonic Scale with a Sharp 4th/Flat 5th added.
The additional tone is referred to as the Blues Scale's Blue Note or Passing Tone, it helps the
pattern to progress smoothly through the tones of the scale.

After the Tonic or (Root)~ note of the Blues Scale, the following notes are separated by; a Whole+Half Step (2)~, a Whole Step (3)~, a Half Step (4)~, another Half Step (5)~, another Whole & a Half Steps (6)~, and a Whole Step to the Supertonic.
The Supertonic [7th, here] is the same note as the (Root), but with twice the pitch; it is one octave up.

A Blues Scale built on the key center of a twelve-bar blues chord progression will work with all three chords of the progression, although a few notes of a scale might sound dissonant over some of the chords.
The key center is like a "center of gravity" of a chord progression, based on the notes from the chords that sound the best together.