  Approximate expressions for correlation functions in binary inhomogeneous
mixtures are derived in a framework of the mesoscopic theory [Ciach A., Mol.
Phys., 2011, {\textbf{109}}, 1101]. Fluctuation contribution is taken into
account in a Brazovskii-type approximation. Explicit results are obtained for
two model systems. In the two models, the diameters of the hard cores of
particles are equal, and the interactions favour a periodic arrangement of
alternating species A and B. However, the optimal distance between the species
A and B is much different in the two models. Theoretical results for different
temperature and volume fractions of the two components are compared with the
results of Monte Carlo simulations, and the structure is illustrated by
simulation snapshots. Despite different interaction potentials and different
length scale of the local ordering, properties of the correlation functions in
the two models are very similar.
