  Extensive Monte Carlo simulations and scaling arguments are used to study the
colloidal charge reversal. The critical colloidal surface charge density
$\sigma_c$ at which the reversal first appears is found to depend strongly on
the ionic size. We find that $\sigma_c$ has an inflection point as a function
of the electrolyte concentration. The width of the plateau region in the
vicinity of the inflection point depends on the temperature and the ionic
radius $a$. In agreement with the theoretical predictions it is found that the
critical colloidal charge above which the electrophoretic mobility becomes
reversed diverges as $Z_c \sim 1/a^2$ in the limit $a \to 0$.
