The 3rd Dieron Regulars use a distinct color scheme, light gray with dark gray trim.

Per FM:Draconis Combine, page 50.

Other references:
Chimera, CB: Miniatures Rules (p 18)
Dervish, CM: Kurita (p 102)


Insignia:

The Dieron regiments bear their district and regimental insignias proudly, along with the House Kurita dragon crest. The crest always appears on the outside of a BattleMech’s right shoulder, and the district insignia of a red starburst against a setting sun appears on the right arm just below it. Regimental insignias tend to appear on a BattleMech’s upper left leg. The various insignias appear in corresponding locations on other types of war machines. The Third Dieron’s insignia is a falcon in flight against the sun. In contrast to most Dieron Regular Forces, the insignia is painted on the lower left side of a ‘Mech’s torso. Per FM: Draconis Combine, pages 48 and 50.