The problem with alot of colourful plants is that they tend to need alot of light and therefore CO2 and nutrients. Especially the plants that have red in them. I can't think of any plants that will keep their red colour in a low light tank. They may grow, but the colour will fade away. There may be some suitable, but off the top of my head, I can't think of any, sorry. The only other way would be to go for different shades of green which if done properly can look fantastic.