This covers all the infantry that wore British uniform, including:
Peninsular War Painting Guides
Peninsular War Painting Guide: British Allies
A rough guide to painting British Allies that served during the Peninsular War – at least those that had unique uniforms. Those allies that served in British uniform are covered by the British Foot painting guide.
Peninsular War Painting Guide: Spanish Infantry
The Spanish Infantry uniforms basically went through four styles, with a constant ragged Campaign option. It is possible that all uniform styles were worn in the same army at the same time.
Peninsular War Painting Guide: Spanish Cavalry
This painting guide covers the Spanish Cavalry of the Peninsular War: