An elder in another hall turns up every Sunday with a spare white shirt - in case the visiting speaker turns up wearing any other colored shirt, in which case he demands the speaker to put on the new shirt!
Ironically, heard this of a congregation where they had white shirts in various sizes, ready in case a guest speaker showed up with another color or design...until the District Overseer showed up in a Blue shirt and was told to change by the COBE. Needless to say, the DO didn't budge and the White shirts disappeared after that.