  We report simultaneous multicolour observations in 5 bands (UBVRI) of the
flickering variability of the cataclysmic variable AE Aqr. Our aim is to
estimate the parameters (colours, temperature, size) of the fireballs that
produce the optical flares.
  The observed rise time of the optical flares is in the interval 220 - 440
sec. We estimate the dereddened colours of the fireballs: (U-B)_0 in the range
0.8-1.4, (B-V)_0 ~ 0.03-0.24, (V-I)_0 ~ 0.26-0.78. We find for the fireballs a
temperature in the range 10000 - 25000 K, mass (7-90).10^{19} g, size
(3-7).10^9 cm (using a distance of d=86 pc). These values refer to the peak of
the flares observed in UBVRI bands.
  The data are available upon request from the authors.
