Via Wilmot Saddle.

This is the recommended route. Follow up Rainbow Stream from Aspiring Flat to where scree and scrub slopes lead up to Wilmot Saddle (1680m). Stay on the true left of Rainbow Stream until the slopes below Wilmot Saddle ease in steepness. From the saddle follow the West Ridge to the summit. Rainbow Valley, like most of the valleys of the area, is subject to avalanche danger in the spring and early summer.