The Colour Glass Condensate effective field theory is a useful framework for studying heavy ion collisions at ultra-relativistic energies, such as those reached at the Large Hadron Collider. In this framework, we study the rapidity evolution of Wilson lines that appear explicitly in cross section expressions. The next-to-leading order BK (Balitsky-Kovchegov) equation for the 2-point Wilson line correlator involves 6-point correlators of Wilson lines. These correlators are typically calculated only in the large-Nc limit. I will present a fully analytic calculation of these correlators in the finite-Nc case, using the Gaussian Approximation. We use these results to find the relative importance of finite-Nc corrections to the next-to-leading order (NLO) evolution equation. I will also present some results from our study of the correlators that appear in the NLO BK equation and the equation itself.