red, with the flag of the UK in the upper hoist-side quadrant and the Bermudian coat of arms (a white shield with a red lion standing on a green grassy field holding a scrolled shield showing the sinking of the ship Sea Venture off Bermuda in 1609) centered on the outer half of the flag
it was the shipwreck of the vessel, filled with English colonists originally bound for Virginia, that led to the settling of Bermuda
note: the flag is unusual in that it is only British overseas territory that uses a red ensign, all others use blue