Watch the Hybrid Scales online guitar lesson by Robert Renman from Blues Booster
This is my own way of viewing 3 useful scales that you can use over the 1-4-5 chords in a blues. All it is, is the Minor Blues Scale for the 1 chord & the Mixolydian modes for the 1-4-5 chords combined. I find this to be a useful concept. Each hybrid scale is very closely related, since the A minor blues scale is present in all 3 of them. Study the neck diagrams and make sure you can "see" how the Mixolydian for A, D and E are combined with the A Minor Blues scale. The scale that is the foundation is the A Minor Blues scale, and the Mixolydian for each chords provides extra color. I find this approach to be very handy when navigating the fretboard. When you know the A Minor Blues scale and the A, D and E Mixolydian, combine them as I explained, and you have lots of great notes to choose from. These are notes you already knew anyway!