“Robert Indiana: Sculpture 1958–2018” (on view through April 16, 2023) features a selection of around 60 works displayed in YSP’s Underground Gallery and at strategic points within its 500-acre landscape. On arrival, visitors can see LOVE (Red Blue Green), the artist’s most celebrated piece, on the brow of a hill. This blood-red cuboid structure is universally known, even to those unfamiliar with its creator. Indiana did not copyright the image, so, since its debut in 1966, it has been used, and abused, in so many forms as to become a cliché. Yet in the open air, the polychrome aluminum work regains a purity that seems to correct its somewhat checkered history.