Responding from the other side (after a fashion)....
My brother got married a year ago last May. They chose not to have a bridal party other than the three nieces between them as flower girls. Fine, completely their perogative.
The invitations and what not were all on white paper with dark purple and bright orange lettering. I took this to be an indicator of their decorating colors (I was right, lots of white with pops of purple and orange in the flowers). As such, when getting my dress for this swanky Chicago wedding, I deliberately did not choose anything purple or orange in color. In fact, my dress was light blue. My mother (brother's stepmom), chose a black, white, and pink skirt suit (very understated, and she did not want to make MOG feel like my mom was trying to step in), DH (then DF) wore a blue suit with a green tie, and Dad wore a tan suit. This all becomes important in a moment...
See, when we got to the venue early for pictures, we found that SIL's sister was wearing a bright orange cocktail dress that looked great on her, and was an exact match for the orange flowers. SIL's brother wore a black suit, much like brother and SIL's dad, while SIL's SIL (brother's wife and mother of a flower girl) wore a deep plum dress with an amethyst necklace. The MOB was wearing a lilac colored suit dress.
What made it painful was the fact that MOB ALSO wore a lilac colored dress (she and MOB coordinated) and my half sister (Brother's full sis), wore a dark purple summerweight dress with the matching chiffon shrug. When I complimented sis on her attire, she stated this was her only "special occasion" dress, which nieces insisted she "wear for date nights" and apparently the wedding. Bottom line was, in all the family photos, my parents and I looked like total outsiders. If it weren't for the fact that brother, Dad, and I look exactly alike (it looks like Dad spit us both out), you'd think we were crashing the wedding.
I don't blame brother, as he doesn't pay attention to color coordination. I don't blame SIL, as she doesn't know the full background of the bad blood between Dad, ex-wife, and sis, and how they drag my mom and I into it at times. However, I did feel like I didn't belong, and I was hurt again earlier this year when sis showed up to my very nice (if not swanky Chicago evening wedding) wearing the casual black sundress and green cardigan she wore to brother's semi casual rehersal lunch the previous May. Guess that purple special occasion dress was only for specific special occasions.
(Please note, ehellions, I've never said a word about this to my siblings or nieces or parents. DH is the only one who knows how much it hurt me to be treated this way by my sibs).