There's really only one "blues" scale which can be used over major or minor blues progressions (1 - b3 - 4 - b5 - 5 - b7 ). However, when improvising in a major blues key you can also use the major 3 to add interest and resolution. Of course, this will not work well when used over a minor blues progression.
Think of it like this; when playing C blues the basic chords are C7, F7 & G7. So you can safely play any note that falls within those chords during those chords and it will sound fine.