  Two sub-samples of blue, luminous contact systems from among 86 systems
discovered in LMC by the MACHO project and classified as EB3 have been
analyzed: a sub-sample of 29 extremely-blue systems (XB) with the observed
colours V-R_C<-0.1 and a sub-sample of 36 moderately-blue (MB) systems with
-0.1<V-R_C<0. To be so blue, the XB systems must be intrinsically very hot and
almost unreddened so that lack of information on reddening is unimportant for
them; their properties offer us a first-time insight into the
absolute-magnitude calibration for massive contact binaries. It has been found
that the LMC systems are apparently not limited by the blue, short-period
envelope in the colour-period diagram which had been established on the basis
of systems observed in the solar neighborhood, in galactic open clusters and in
the sample of Old Disk systems in the direction of the Galactic Bulge. The
period - magnitude correlation for the XB systems has a similar slope to those
established in the absolute-magnitude, B-V and V-I_C based, calibrations for
W~UMa-type systems.
