In 1707, new ensigns were established for the Royal Navy. All ships were ordered to fly the Union Flag as a jack and each squadron was given its own ensign displaying the First Union Flag in the canton. (In 1801 the diagonal red Cross of St. Patrick was added to the Union Flag.) These Red, Blue and White ensigns were used until 1864. In that year, the Union Jack and the White Ensign were reserved for the Royal Navy, the Blue Ensign was reserved for the use of qualified Royal Naval Reserve officers in command of merchant ships, and the Red Ensign became the British merchant ensign.

What about frigates and sloops on solitary cruises that weren't attached to squadrons? What flag would they fly at the stern? I know most wouldn't have anything flying until right before engaging, but since most of my ships are at quarters I want to show colors.