I've never been a bridesmaid, but I am a bride to be. I'm SO glad that you came to an awesome compromise on the dress.
My colors are black white and red, and my maids will be in black. I don't care what style the dress is (halter, strapless, etc) as long as it's black, and has a satin-y finish. I'm leaning towards tea length, but I don't know that I'll ask them all to wear the same length. I figure everyone needs a little black dress, so they might as well get a dress that they LOVE and will be able to wear a lot after my wedding