I think the purple is going to be gorgeous--just as an aside, while I was dealing with the shenanigans that wanting to wear a brown dress created, my friend (who also happens to be a top salon stylist and flies all over the world doing celebs and royalty's hair) told me that colour is the new white and that it "would be gorgeous, darling". (Yes, he really does talk like that!) So I say go for it!
I found that compromising where I didn't care (for example, chair covers--I could give a toss, my mom thought they were essential, ehh, whatever) was the best route and holding firm was the name of the game. Honestly? NONE of it really has to do with the wedding. The stress of planning such a big public event just seems to bring out those little holes in people's psyches. I'll recommend indiebride again (just google search for it), they are a caring and AWESOME community and really helped me come up with a funky and fun time.
To make you feel better, my mother and my sister had this conversation. In front of me. At my dad's birthday dinner.
Sister: I don't know what to wear! It's a mid-afternoon wedding, but I want to dress up. But I can't be as dressy as if it was an evening wedding.
Me: Wear whatever you want. Honestly.
Mom: Well, you don't want to show up the bride. And Jennie's dress is pretty basic.
Sister: Yeah, I don't want to look better than you.
Me:
Just don't try and marry Pete. That would really freak people out.
Sorry so long--but in the end, everyone had a great time! My mom can't stop talking about how fun it was. And I LOVE my brown dress.