All Ryuken units paint their BattleMechs charcoal gray. The members of Ryuken-yon adorn their 'Mechs with dark blue accents.
Per FM:Draconis Combine, page 129.
Tai-Sho, CB: Miniatures Rules (p 18)
The Ryuken apply the Kurita dragon crest to their BattleMechs on the left leg just above the knee and near the exhaust ports of fighters. The Ryuken insignia is a dragon curling around a Katana sword, both drawn with rich detail. The regiment's insignia is a full moon emerging from backlit clouds. Per FM: Draconis Combine, pages 126 and 129.