Marfa, Texas, the shooting locale for the George Stevens epic film Giant 70 years ago, is known as a dot of cultural sophistication, big on minimalist art, amid hundreds of miles of Texas brush and desert. It’s also renowned for the Marfa Lights, a nocturnal phenomenon of distant brightness that can appear orange, yellow, blue, red. It’s not known as a hangout for anxious thirtysomethings yapping about politics, gender, and muddled friendships, but that’s the upshot of Very Blue Light, Daphne Silbiger’s new drama at The Tank. That it plays as well as it does is a tribute to Silbiger’s clever invocation of familiar themes, and a beguiling cast of four up-and-coming actors.