I love the new iPhone colors, they're different and exciting when everyone else is... sleep-inducing gray or black or generic pastels where most of the time they're out of stock. Everyone also does silver and everyone does pale/muted/desaturated/pastel hues. It's lovely to have some choices.
It's very nice seeing bolder colors again; and adding case over that allows some contrast as well as reducing the chance of scuffs or breakage, even on the most robust models. A brown or green case, especially with black bezels, for the orange phone really pops. Or, again with using black bezels (when possible) opposite using gold, green or orange case for the blue phone, for two examples of many pleasing combinations. The blue phone with a clear case having black bezels with Qi/Magsafe gold rings look truly stunning.
Clear cases, those with high enough drop ratings with raised lip around the edges ( >= 3mm recommended, especially for tarmac surfaces such as parking lots) really showcase both color and complement beautifully. Silver being neutral will go with anything so get one that looks like a bunch of overlaid "dizzy daisies" from the late-60s imprinted on it and voila. Actually, the translucent color isn't a factor as much as the material is, but usually it's the edges and lip going over the surface are what count by far the most. The backing material could otherwise be plastic, titanium, kevlar, kryptonite, etc, as any of those help against even minor scuff risks (but obviously stronger material for the backing lessens the chance of scuffs or breakage that much more). Titanium vs kevlar is a chapter in of itself...
Of course, if every phone was just black or just white, the cases all have those hues to choose from, but the phone having the color with case offering the contrast just looks best, IMHO, YMMV, EIEIO, etc.
What bugs me most, is how many cases don't offer enough cushioning, thinner lip, incomplete chassis coverage leaving areas exposed*, with other customers also reporting that their $90 case either felt cheap, didn't feel snug against the phone, scratched the phone because the hard plastic was against the metal instead of the softer material, and/or the cushioning material didn't protect well enough from a 5' drop and now they have a spider web-shaped crack from the corner, making the task of finding a proper case even more fun. At least for some, others get frustrated.
* which can be good or bad, depending on heat dissipation requirements based on how the phone is engineered, as long as the main components and microchips get enough heat moved away from them to prevent throttling, that's the main issue. Not letting the chassis get so warm that you can fry an egg on it is the next consideration and on my Android that's happened a couple times, especially when in full sunlight.
