A good one would be the Hanoverian Legion:

If you're feeling that's too much red, then paint them in their greatcoats. The regiment's commander requested that they be allowed to wear them at Bussaco to avoid confusion.
Another favorite of mine is the Legion du Midi:

Conveniently, they are in the same brigade (1st Brigade: General of Brigade Edouard François Simon) of Loison's Division, along with three battalions of the 26 Ligne.
If that doesn't suit your fancy, then there's always Laval's German Division for Talavera. JJ's Wargaming Blog gives a good OB here:
http://jjwargames.blogspot.com/2014/10/napoleons-german-division-at-talavera.html It's Badenese, Nassauers, Dutch, Hessians and Frankfurters, in all kinds of colors.
Then there's always Suchet's Army in Aragon to draw from. Here's a good order of battle:
http://napitalia.org.uk/eng/sagobf.shtml You have French, Italians, the Vistula Legion, Neopolitans, French Cuirassiers in brown uniforms, al kinds of fun.
A good book to get is Military Dress of the Peninsular War, by by Martin Windrow and Gerry Embleton. There's 100 different color plates, showing just how varied a uniform things could be.