Bridesmaids Jewelry?

I have been planning to buy my bridesmaid their jewelry for the wedding as part of their thank you gift but I am having difficulty. My wedding colors are red, white, and gold, I am probably going to be wearing white gold/silver with my dress, and they are wearing red dresses. I can't decide if I should have them wearing the same color jewelry as me or I should have them match the theme. I have considered just asking them, but I kind of wanted to surprise them. So, I would love some advice on this. Another thing I am struggling with is finding nice jewelry at a reasonable cost I have 6 bridesmaids so it adds up quickly, and I don't want to get them something that will turn green, so ideas on where to look for things would also be so helpful!