Fair warning, this one’s a little out of our normal range of expertise. This is what I’ve been told, and read, over the years, but I’m not an expert, so you’ll probably want to supplement this with some of your own research.
I’ve always been told that dark blues are the best option. Pure blacks create a clear profile, even in very dark conditions, while dark blues will start to blend in with the background. From what I remember, in low light, the eye starts to have issues distinguishing between specific colors. Dark blues are, apparently, the hardest range of colors to properly distinguish in low light.
The general idea with camouflage isn’t (exactly) to blend into the background. It’s to fake out the brain into ignoring an object by denying it a clean border. Basically, your brain processes the objects around it by seeing the edge or outline of something and then figuring out what it is off of that. When camouflage disrupts the outline, your brain has a much harder time figuring out that something’s there, even if you can actually see it.
Greens and browns can be really useful for camouflage, depending on the environment. In an urban one, however, green is probably going to work against you. In some ways, green is the exact opposite of blue, your eyes are unusually sensitive to variations. So, while a dark blue is hard to separate from that concrete wall, a dark green one should be really easy to identify, even in the same light.
Now, as to those colors being harder to identify in daylight, in an urban environment? Maybe. But, ultimately, if someone’s going to misidentify a color as black, it stands to reason that most people will. Dark clothing tends to stand out during the day, and there isn’t much your character can do about that.
The time when color misidentification becomes significant is when there’s nothing else to go on. Like the grey suited villains in Michael Mann’s films. “It was a guy in a grey suit with a beard,” is a lot less useful than “it was a guy in a black shirt”, even when that shirt turns out to be very dark blue.
I used to have a tie that had iridescent strands, in bright light they’d look electric blue, but in dim light they’d look black. On first thought, it sounds like a good option, but, I wouldn’t recommend it, because you don’t want your shirt lighting up like a signal flare any time you get near a light source. Additionally, while iridescent fabrics aren’t exclusively in the realm of bad 60’s sci-fi movies, they’re still uncommon, so your character would be painfully memorable on the street.
If you’re working with a sci-fi setting, there’s already been some serious work on paper that can self print. The way this works is you have tiny beads that are white on one side and black on the other, by running an electrical current through them, you can cause them to rotate, instantly displaying a message. The tech’s probably about five to ten years away from anything practical, and as far as I know, no one’s suggested using it in textiles, but if your story is twenty (or more) years from now, that might be an option.