A useful harmonic-melodic conception of the basic major Blues chords (I7-IV7-V7) is as three sets of matched “scale-chords” or “chord-scales”…
The C7 chord (I7 in the key of C) is paired with the C Mixolydian scale…
The F7 chord (IV7 in the key of C) is paired with the F Mixolydian scale…
The G7 chord (V7 in the key of C) is paired with the G Mixolydian scale…
Now lets’s play each scale-chord pairing over a typical twelve bar blues form– and notice the unique sound-feeling that each pairing creates–individually as well as within the harmonic context of the entire form…
Time and time again, you are going to rediscover that scales and chords are intimately inter-related. Knowing your chords helps you know your scales and vice versa! Understanding such scale-chord relationships–theoretically, by sound-feeling, and by visio-spatial layout on the keyboard–lays a solid foundation for fluent improvisation and pays huge dividends when reading, transposing, and playing by ear!
Homework
Using your ears and your knowledge of scales and chord structure, play these scale-chord pairings in all keys that you expect to play in. In doing so, you are going to build an enormous chord vocabulary that integrates theory, ears, eyes, and muscles–laying a solid foundation for fluent improvisation.