Watch the G7 Blues online guitar lesson by Rob Garland from Melodic Soloing: Blues Chord Tones
What are chord tones and why should we use them on a blues? Chord tones are exactly what you think they are, the tones that make up chords!
For example, take a G7 chord, the I chord of a G blues: the chord is made up of a root, a 3rd, a 5th, and a b7th named as intervals from the root. This gives us the notes G-B-D-F. Those are your chord tones.
A dominant chord is made up of a major 3rd and a b7th. So, a G7 has root-3rd-5th-b7 (in relation to the major scale). A standard I-IV-V blues has 3 dominant chords. So, a G blues has the chords G7-C7-D7.