The cataclysmic variable AE Aquarii: B-V colour of the flares
  We report simultaneous observations of the flaring behaviour of the cataclysmic variable star AE Aqr. The observations are in Johnson B and V bands. The colour-magnitude diagrams (B-V versus V and B-V vs. B) show that the star becomes blues as it becomes brighter. In our model AE Aqr behaviour can be explained with flares (fireballs) with 0.03 < B-V < 0.30 and temperature in the interval 8000 < T < 12000. 
R. K. Zamanov, G. Y. Latev, S. Boeva, S. Ibryamov, G. B. Nikolov, K.   A. Stoyanov
astro-ph.SR astro-ph.HE