All Ryuken units paint their BattleMechs charcoal gray. Ryuken-san warriors do not accent their vehicles with any color.
Per FM:Draconis Combine, page 128.
Panther, CM: Kurita (p 104)
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. Ryuken-san warriors display the Kuritan and Ryuken crests and the Reyuken-san regimental insignia, a narrow gold line that sketches out an angular dragon’s head across each ‘Mech’s torso. Per FM: Draconis Combine, pages 126 and 128.