  We investigate the validity of Fluctuation-Dissipation (FD) relations for a
mixture of two granular gases with different physical properties (restitution
coefficients or masses) subject to stochastic driving. It is well known that
the partial granular temperatures T_1 and T_2 of the two components are
different, i.e. energy equipartition is broken. We observe, with numerical
simulations of inelastic hard disks in homogeneous and non-homogeneous
situations, that the classical equilibrium Green-Kubo relations are satisfied
separately for each component of the gas, the role of the equilibrium
temperature being played by the granular temperature of each component. Of
particular interest is the limit in which one of the two components consists of
only one particle, representing a non-perturbing thermometer. In this case it
turns out that such a thermometer is measuring its own temperature and not that
of the surrounding granular media, which in general will be different.
