The one on the left and right are from Becoming Jane (2007) and the middle is Pride & Prejudice (2005). Something about blue just seemed to make both costume designers very happy.

I would also not be impartial to a return in the men's fashion. Check out James McAvoy in Becoming Jane. or mebbe they should just host more period themed dances
If you need more pictures to look at, just google search images, some pretty nice white dresses from the dances (there's a trend to these colors) o, and these images were found through google, can i get sued for this? well, just in case, i do not own these pictures and thank kindly the websites connected through google search that do own them:)