Hmm...this is a question of personal preference for colors. I like lighter colored strands with green and blue so my vote goes for fourth strand when counting from the botton of the picture.
It seems like your budget is 500-600 range. I think this strand is also a worthy contender
What's your wife's complexion? Certain colors pop up more on certain complexion. I am olive skin tone and although peacock overtone is pretty, the ones with more green or very strong pink pop more on me. The pink from light peacock strands' disappears on me, same as light blue. Bright green such as fly's wing are pretty on most complexion, imho.
I love those very round pearls, I think you should firstly figure out whether your wife is into a round or relatively oval one, and whether she is into relatively bigger pearls or smaller, Well, I love round and big one, then I would choose the 11th, or perhaps the 9th which might be more suitable to go well with any suits.