Colours of the flickering source of Mira

We report photometric observations in Johnson UBV bands of the short term variability of Mira. The amplitude detected is 0.16 mag in B band. Adopting interstellar extinction E(B-V)≈ 0, we find for the flickering source colour B-V ≈ 1.3, temperature T ≈ 3700 K, and radius R ≈ 0.77 R_⊙. The colour of the flickering source of Mira B is considerably redder than the average B-V colour of the flickering in cataclysmic variables and in the symbiotic Mira EF Aql.