According to William S Biles - Uniforms of the SYW - a painters guide and A History of the British Army (Fortesque?)
Household Cavalry - Horse Grenadiers - 2 companies.
Red coat, blue cuffs, buff vest & trousers. White lace, gold buttons.
1st Company - buff shoulder belt with 2 red stripes. Mitre cap - front blue, rear red bag & lower portion.
2nd Company - buff shoulder belt with 2 blue stripes. Mitre cap - front red, rear blue bag & lower portion.
Shabraque & pistol housing - blue with yellow border & single red stripe within border. Insignia on pistol holsters and rear corner of shabraque was crown over garter with GR within garter.
I can scan the relevant pages and send to you if you want.