I like the uniqueness of the copper, although that's becoming less and less true, as Nissan's not the only one doing it.
I never have problems finding it in a parking lot, except one place I go, where there's another copper Murano! But I've walked through a parking lot and ended up next to a silver Murano, without realising until I'm right there. Silver blends in with all the other silver, so it doesn't stand out. Depending on your personality, that could be a good thing or a bad thing. But it really glistens in the sunlight, more than most silvers I've seen.
I find the lighter colours, such as silver, gold, copper, white, and even pewter, etc, really highlight the styling of the Murano, with it's upswept window line. I've always been partial to the impact orange and black gives, especially at Halloween, and on my 1972 Kawasaki 500 triple, so for me, the copper brings back very fond memories.
I love the blue as well, as I always liked that colour and the black is sharp, especially when clean, but suffers from the usual black colour issues, which may or may not be a problem, depending on how busy your life is, and where you live. The one thing I do find with the black, is the black window frame tends to get lost in the colour at a distance. This is good if you aren't keen on the styling of the windows, or you want that all black look. I would be tempted to change the grill or paint it, if I had black, as every time I see a black Murano, my eyes are drawn to the grill and it's actually a little distracting. Not an issue from the side or the back, just the front. It reminds me of a kid with braces, yet on other days, it's really sharp looking. I think if you keep the bling OEM grill on the black, you really need to offset it with bling chrome wheels.
I too was worried about the copper getting "old" and getting sick of such an intense colour. After two years of copper, I'm still in love with it, and it still looks fabulous in any setting. It's a sportier look than most, without doubt. If you are going for a classy look, instead of a sporty look, then I'd probably go for a platinum, silver, pewter...
It all depends on what's important to you, which colour is right. There is no wrong colour Murano, but you have to get which ever one makes you smile the most when you see it, and not worry about tiring of it. If you truly pick the one that makes you the happiest, it won't get old or tiring... I wouldn't worry about what other people like, get what YOU like. What's more important, getting in it and thinking "Yeah, Baby!" for years, or a someone else's perception of it, when it's time to change, one day?
My 2 cents (pence) for what it's worth....