A forged Robert Motherwell painting was branded with the equivalent of a scarlet letter on Tuesday in a legal settlement involving three art galleries and the Dedalus Foundation, which owns the copyrights to Motherwell’s works. “Spanish Elegy,” the painting at the center of the dispute, was sold to a European gallery, Killala Fine Art, for $650,000 in 2007 by Julian Weissman, who had previously worked as a salesman at Knoedler & Company in Manhattan. Before the sale Dedalus initially concluded that “Spanish Elegy” was authentic, but later backtracked and declared the work, supposedly painted by Motherwell in 1953, to be a fake. The Killala gallery said in its lawsuit that it had relied on the foundation’s assurance in making the purchase.