  The individual motion of a colloidal particle is described by an overdamped
Langevin equation. When rotational degrees of freedom are relevant, these are
described by a corresponding Langevin process. Our purpose is to show that the
microscopic local density of colloids, in terms of a space and rotation state,
also evolves according to a Langevin equation. The latter can then be used as
the starting point of a variety of approaches, ranging from dynamical density
functional theory to mode-coupling approximations.
