Above is an actual case in point. A real wedding. Katie's bridesmaids chose their own styles of tangerine or strawberry-colored dresses. Her sister, the maid of honor, wore an ivory bolero to stand out.
Another way to keep everyone linked is to purchase a fabric you love in bulk (enough for all your maids). Have them all go to the same designer or tailor to have a dress made up. Though you'll have different styles, maybe some with cap sleeves and others sleeveless, it's okay because the fabric will be the factor joining everyone together.
Don't want to bother with tailors and fitting appointments? Well, if you can believe it, the quartet above are all wearing the same dress. I didn't believe it until I studied out the Two Bird website. The designer offers 11 colors and each dress in the collection can be worn ten different ways. Wowzer! This is one of the best solutions to the bridesmaid dress dilemma I've seen yet. Kinda like the best thing since sliced bread.