The Nightriders paint their 'Mechs and vehicles ash gray with silver trim.
Per FM:Capellan Confederation, page 87.
Goblin ISV, Classic Battletech Master Rules Revised Edition (plate 5)
They all display the Confederation crest in addition to the Cavalry emblem, an armored knight with a red plume in his helm rising from a green triangular field. Each regiment except for the Wild Ones also displays a regimental insignia, usually on the back of the shoulder or the upper leg.
The regimental insignia is a fire-breathing, mechanical black horse galloping over a green field.
Per FM:Capellan Confederation, pages 86 and 87.