Black tends to make dust and dirt buildup noticeable. White and lighter colors tend to 'blend' it in a bit more with the exception of the more darker, concentrations of dirt. Dark colors like dark blue, black and deep greens contrast to the 'brown' or tannish colors of normal every day dust/dirt.
I recommend Jane Seymour...she has looked nice as she has aged... But as far as color? Get what you like. And that's so subjective to the individual how can I or anyone really offer an opinion. One Mans, White Blizzard Pearl...is another Mans boring White.... One Mans Sharp looking Black...is another Mans hard to clean nightmare.... In the end...look at the vehicle....do you like it? ...Okay...go for it...
As to the best Prius Color, I would make a couple of observations. First, I spend remarkably little time standing outside of my car staring at its color. Second, you cannot see the exterior color of your Prius from the inside. So I must say that the color I choose is ultimately not going to be for MY pleasure. Therefore, I choose my color for its visibility to other drivers on the road. If I could, I would choose electric orange or some other equally visible color. The Gen III Prius comes in seven colors. Six of them are variations between white and black, concentrating on shades of gray. Next time your are out driving behind a gray/silver car, notice how little contrast there is between that car and the pavement it is driving on. Gray/silver cars are the LEAST visible cars on the road during fog, at dusk, in rain or snow and therefore among the more dangerous from a visibility standpoint. So my recommendation is buy a color that can be easily seen by other drivers.
White is about $200 USD extra. I just bought white, and like it. Visibility is important to me, and I thought white was more visible. However, I will comment that the huge SUV that showed up in our blind sport that caused my daughter to wreck our last car, a Crown Vic, was a white SUV. Glad to hear the "safety orange" comment. I, too, have an engineering mindset that would go with neon green, yellow or orange. However, our culture does not support that. Even fire/rescue here in the US went to the safety colors only briefly, then returned to the less visible reds.
Color is such a subjective thing. Just curious... are you counting Nautical Blue and Seaglass Pearl as gray? Having seen both, I would not group those colors with the black/white/silver/gray set. Choosing to drive with DRLs (if available) or headlights on can also add to visibility, no matter the color of the car. It pays to drive defensively, not assuming that another driver sees you. And all cars are the same color after dark (to borrow a phrase). I'd choose lime green if I could get it, because I like that color. I chose Seaglass Pearl instead, because it was the closest to lime that was available (and it's not even close). I really love it, though. And, although I don't spend a lot of time outside staring at my car, I know it looks good. I don't spend much time staring at myself in the mirror, either. But that doesn't mean I don't care how I look.
Before I considered a Prius my neighbour had an old shape black one. It did not notice that it was old shape or an ugly car. I could get away with an old shoppe if it is a black one.
I'd also add gray to the list of classic car colors. Another color that's pretty easy to maintain and hides dirt well.
So, I'm in the same decision making process, but I'm at a disadvantage, as I'm hunting for used/certified. But... Here's my run down on color... I LOVE the black. I think it looks the best. It's sporty and classy and kinda badass all at the same time. (I'm a biker, and like badass/black stuff.. hehehe). BUT... a good friend of mine bought a beautiful black Mazda6, and while she loves her "Leon," she will never buy another black car ever again. I once had a 1996 Geo Prizm (Toyota Corolla) with the Black Sand Pearl. That is still my favorite car color, ever. If they offered the Prius I'd get that in a heart beat. But the non-metallic black looks like it will show every knick, buff mark, and spec of dirt/towel lint, that keeping it looking as good as it's supposed to will be a challenge. Also, I happen to really like the "bisque" interior, and that seems to be impossible to find with the black exterior. So, moving on. I actually really like how the red looks on the Prius. But, I just can't do red. I'm a Minnesotan. We don't like to draw too much attention to ourselves.. hehehe. I also think the blue is fun, but I'm trying to make a "Lexus" out of my future Prius, so blue doesn't have that "fancy" feel. I once loved any car in silver. Today, when I see silver, I think "rental car." To a lot of people, when they see white, they think "rental car." But I am pretty sure I'm getting the white. There are lots of them, for one... and there are more white ones with the tan/bisque interior than any other color. So, Blizzard White Pearl/Bisque is officially my target combo. Which is the same exact color combo of my car before the smart, a 1995 Nissan Maxima SE. Interesting..... (thanks for letting me think that out aloud!)
I'm not really a fan of white, black, and silver/gray, mainly because so many cars are that color. When we were looking at getting a C, Summer Rain Metallic was the color we were likely going to get (habanero was too much for my wife ). Then we found our Gen2 in white and it was perfect in every way besides the color. One nice thing is that it doesn't show dirt or scratches/dents very well, especially from a distance. There were a few small dings on ours that I didn't even notice for the first few minutes of looking at it. We haven't even washed it since we bought it last June. It just doesn't look bad enough for it to be worth it to me to wash it. I got to make up for the white car with my green Insight, though.
I prefer blue or red and only buy those when I have a choice. I have owned a blue Prius for about two years and find that, so far, it has retained its look very well. White, grey, tan just seem super boring to me. It all is a matter of opinion really. Choose the color you like.