Coordination by sunspots: Letter is mightier than colour

We set up an experiment to test whether players use a payoff-irrelevant public message (BLUE or RED) as a possible sunspot to coordinate in a Battle of the Sexes game in which the strategies are labelled X and Y. We find that players do not play a sunspot equilibrium, instead learn to coordinate on a particular focal point (strategy X) in the game, even in the presence of the public signal (colour) and stick to this focal point, after the public signal is withdrawn.