In recordings that date back as far as 1929, Walker can be heard working "color tones" like the 9th into his blues riffs; a technique that guitarist Stevie Ray Vaughan explored extensively over 50 years later. The above short example of a T-Bone Walker riff, starting on bar 9 of a blues in G, should illustrate the guitarist's interest in color tones.
Notice Walker's use of the third - a B natural (often bent or hammered to from Bb) on the G7 chord. T-Bone correctly chooses to avoid the B natural over the C7 chord this would sound "wrong")instead switching to Bb. Walker highlights the A natural on the third bar of the phrase, and the note stands out as a nice contrast to the blues scale ideas that he played earlier.
Playing like T-Bone is a challenge - it takes a lot more than simply knowing your blues scale. A great ear, and a lot of patience and hard work is required.