4' tall and dark - I start red hibiscus from seeds each year and they get at least 4' and probably more.... although they're probably perennial in your area? But nice, maple shaped leaves in dark red.
There's also a number of red colored Pennisetums - red fountain grass - and I think they also come in various heights. Might be a little wide for your area, though.
If you're into seed starting, Summerhill has a purple millet:
http://summerhillseeds.com/mil...
Or.... chocolate Eupatorium???http://summerhillseeds.com/eupatorium-rugosum-chocolate-p-245.html?cPath=68
Whoa, I'm on a roll!
