Although the subject of uniquely painted A-20 (i.e. favorite paint schemes) was covered over a month ago a source of mine in the UK has forwarded some interesting info on the Royal Navy usage. The RN received 36 Boston's from the RAF of which 21 were the Turbinlite model. The aircraft were not utilized in combat operations but were assigned to radar calibration duties for both ships and airfields. There was some use in TAG training (Telegraphist-Air- Gunner) as well. Most of the aircraft were assigned to No. 771 squadron based at RNAS Twatt and Halston in the Orkney Islands.
The aircraft were repainted in typical RN scheme (grey and green) with sky undersurfaces. As you can note from the photo below the expression "Royal Navy" can be vaguely seen on the aft fuselage just forward of the horizontal stabilizer. The expression "T8B" is in yellow and "T" stood for RNAS Twatt. RNAS Ayr and Arbroath used the leading letter of "A" (e.g. "A9R").

A Royal Navy Photo