  We explore the subleading-N_c corrections to the large-N_c Balitsky-Kovchegov
(BK) evolution equation by comparing its solution to that of the all-N_c
Jalilian-Marian-Iancu-McLerran-Weigert-Leonidov-Kovner (JIMWLK) equation. In
earlier simulations it was observed that the difference between the solutions
of JIMWLK and BK is unusually small for a quark dipole scattering amplitude, of
the order of 0.1%, which is two orders of magnitude smaller than the naively
expected 1/N_c^2 or 11%. In this paper we argue that this smallness is not
accidental. We show that saturation effects and correlator coincidence limits
fixed by group theory constraints conspire with the particular structure of the
dipole kernel to suppress subleading-N_c corrections reducing the difference
between the solutions of JIMWLK and BK to 0.1%. We solve the JIMWLK equation
with improved numerical accuracy and verify that the remaining 1/N_c
corrections, while small, still manage to slow down the rapidity-dependence of
JIMWLK evolution compared to that of BK. We demonstrate that a truncation of
JIMWLK evolution in the form of a minimal Gaussian generalization of the BK
equation captures some of the remaining 1/N_c contributions leading to an even
better agreement with JIMWLK evolution. As the 1/N_c corrections to BK include
multi-reggeon exchanges one may conclude that the net effect of multi-reggeon
exchanges on the dipole amplitude is rather small.
