I've been to weddings where the bridesmaids had the same style of dress, but in different colours. My favourite was one who had 5 bridesmaids and the colours were navy, yellow, orange and purple. The flowers had all the colours together but it really was such a bright and cheery bridal party.
Unfortunately I agree that the bride should have the last say, seeing as it's really the bride and groom's day afterall.
However, for my wedding, I did make sure my bridesmaids (2 sisters and SIL) were happy with the dress (seeing as they paid for it), and I chose colours and styles that did actually look good on all 3 of them. I just thought that was the nice thing to do.
But, not all brides think like that!! My sister was a bridesmaid and the dress was so bad. She was made to wear a tight, light coloured dress which looked so yuck - and she's not a small girl - every buldge and roll was on display for the whole workd to see!!!

It only looked good on one girl.. who had no fat on her at all!!
LOL sorry for the tangent.... im bored at work