The list below are all plants that would add color. They range in the yellow, pink, orange, red range. Limnophila Aromatica hippuroides is especially striking as the top portion of each stem is a very bright med pink. Telanthera is fairly easy to grow and the under color of the leaves are a fairly bright pink. If you want something in the orange range my first choice is Proserpinaca Palustris followed by Myriophyllum tuberculatum. Nesaea pedicellata 'Golden' is beautiful but is not the easiest plant to grow but has a great true yellow color. Rotala macrandra goes to the red range, I find it easy to grow but many people have trouble with it. It likes lower nitrates (try to keep mine at 10ppm) and slightly higher phosphates (try to keep mine at 1.0ppm) and alittle extra micro nutrients. Rotala Wallichii likes softer water, grows like a weed and the upper portions of the growing stems are a nice light pink color. You can also do a Red Tiger Lotus but as they grow they tend to take up alot of room so wouldn't recommend one for your tank.
Telanthera Rosefolia (Alternanthera reineckii)
Limnophila aromatica 'hippuroides'
Proserpinaca Palustris
Myriophyllum tuberculatum
Nesaea pedicellata 'Golden'
Rotala macrandra
Rotala Wallichii
As for carpet plants if you want a really low one you might be able to do Dwarf Baby Tears. In my 220g I have Pogostemon helferi which can grow in medium light. Its a bear to get going because it has shallow roots but once you get it going it is really unique. Another thing is if you want a small plant/plants for foreground accenting Crypt Parva is great. It only grows about 2 inches tall and works really well as an accent for rocks or DW. There are a ton of other plants but the ones I listed are ones I have personally grown.