About Rainbow Lake
Rainbow Lake asks for a hard outing by this site's scale, with 7.5 miles listed one-way from Bear Lake TH (off-trail). The lake itself sits at 11,742 feet in Continental Divide / Flattop Area.
The listed approach is 7.5 miles one-way from Bear Lake TH (off-trail), but this should be treated as a route-finding objective rather than a simple maintained-trail hike. It is an off-trail objective, and the setting is near Stones Peak. In this area, this divide country is remote, high, and often more about navigation than maintained-trail hiking.
NPS describes Rocky Mountain National Park as spanning more than 415 square miles, and this divide country sits in the kind of interior terrain where mileage, elevation, and navigation all matter.