I don't have a dark vehicle. But I have been using nothing but RainX premixed orange stuff since before 2000. I use it in my washer container and keep a couple of spray bottles around for house windows and car windows.
You may not be impressed with it at first but the more you use it the better it gets. My windshield on my 01 Sentra with 101 K miles looks like a new windshield.
It might not be the RainX but I'm not about to to take a chance on anything else.