As mentioned, some of the Crypts would work. I like Cryptocoryne cordata var. blassii as it has a different leaf shape from the common C. wendtii.
Ludwigia glandulosa has a nice deep red color throughout the stem. I'm able to keep it in a 20 gallon with 65w CF, soil underlayer and only dosing gluteraldehyde (Excel substitute). It grows rather slowly and has a deep maroon color for me rather than the bright purple-pink of the plantfinder picture.
Limnophila aromatica might be too big and bushy but has lovely pink leaves near the top in the 20 gallon I mentioned before. Many Rotala species and other Ludwigia species would most likely work but many of them tend to grow fast so you'd have to keep up on trimming them. There are quite a few red plants listed in the PlantFinder. See
here - I couldn't link straight to the red list, so go to "Aquascape Placement" and select red for the list.