Are there 3 chords in the basic blues chord progression?

No, the basic blues chord progression is based on only 3 different notes: the tonic, subdominant, and dominant chords. In blues notation, the progression uses the numbers I, IV, and V to represent these chords, with the basic progression being I, IV, I, V, IV, I.

These numbers correspond to the scale degree of the root notes of each chord in relation to the tonic. The tonic chord (I) is built on the first degree of the scale, the subdominant chord (IV) is built on the fourth degree, and the dominant chord (V) is built on the fifth degree.