This next photo is from a wedding I was in. Our dresses were from DAVID'S BRIDAL. The wedding was in March. Look at how those colors pop!
If you are going the department store route, better items can often be found in the regular dress section than in the wedding specific region. This next dress has a color that I would classify more for summer, but the flowers give it a springy feel. It can be found at Macy's.
Ann Taylor offers some classic styles.
I am actually a fan of finding dresses at non-wedding locations. You can often find something that you truly like and that your attendants will, honestly, be able to wear again. Recently, dresses with prints have become popular. Check out this Spring print from Anthropolpgie. Wouldn't it look fab with a daisy bouquet?