Bridal party color

Ladies, color suggestions welcome! Let me start by saying that I am not very good at decorating or pulling together outfits and making things look very put together. I’m having an evening October wedding in Southern California and I want it to look classy and elegant. I’ll attach a picture of my wedding dress which the top is kind of an ivory lace with a little sand undertone it’s not quite champagne. The bottom of the dress has that same undertone underneath organza. The factor that is making this hard for me is that I’m only having one bridesmaid /matron of honor, my sister and then there will be the groom of course with one bestman. I would love to see the groom in a navy suit as well as his best man and he’s OK with that idea. I’m open to a black suit as well. The problem is the dress for my sister, the bridesmaid. I want a color that will stand beautifully beside my Ivory/sand dress and she’ll be standing right beside me basically and she’ll be the only person on that side of me. I’m just wondering if a color on the completely different spectrum will look odd and out of place. I don’t like the idea of any color that looks similar to my dress like ivory, beige, gold etc. I’m old fashioned that way. I love blue and so does my sister. I’m think more like an ink blue or Aegean. I’ll attach a photo. But will that color look odd with only one bridesmaid and what suit goes with that. I feel like navy won’t look nice beside it.??? Am I wrong? I could do navy dress but then what suits? I don’t want grey beside the ivory wedding dress.