In well-timed contrast to climate activists who claim to defend nature by defacing art, the American Tonalist Society is presenting a painting exhibition in which reverence for nature is defended in limitless — and lovely — shades and majestic glory. Rosy-fingered dawn, as well as purple-edged marshes, sun-dappled creeks, and assorted scenes that expand the tradition of tonalism are on view at the Salmagundi Club through May 7 in “Shades of Gray: II.”