DesignMaster Tint-It floral dye sprayed on the adhesive side of the film is very lightweight. I used 1.3mil D&K lamination film. The spray dye didn't seem to affect the adhesion of the film to the balsa. I used this method on my Trailblazer plane.
The yellow I used on this plane is (heavy) rustoleum. There are definitely lighter color options and methods other than rustoleum. Dope, Klass Kote epoxy, Nelson/system3 would all have the potential be much lighter than the rusto paint.