I can see why giving yourself a bit more creativity with the colors can make for a more interesting oc. Though, I have to disagree with the notion that natural colors are boring. I've seen plenty of brown and gray and tortie designs that are far from it! Look up some designs for canon characters and you'll see the creativity, even with the limited palette of reality, shine through.
As for the oc creation, I don't have an image yet, but I'm going to make one and send it over when I can. I do have a basic description for them.
Their name is Dancingleaf. They're a white nonbinary medicine cat with honey-colored eyes and paws that were stained with color, primarily green, from all their work with plants. They've taken these stains as a mark of all the hard work they do for the clan, and their fur has become so stained that washing their paws is a futile effort.
Dancingkit was born and raised in WindClan and was a very messy kit. They could be mistaken as brown or gray from a distance from all their rolling in the dust. Their messy nature didn't fade as they got older, just became a bit more purposeful. They took the role of medicine apprentice during a time of high tension between WindClan and SkyClan, and spats were common. With so many injured cats, many herb poultices had to be made and used. The pressure of so many cats left Dancingpaw not being all too careful about keeping their paws clean. So the pulps lingered and soaked into their fur, over time dyeing their paws green, yellow, blue, and so forth. By the time they'd earned their full name, the color may as well have been permanent.
I'm not all that used to making unnatural ocs without a natural reason behind them (My closest one aside from Dancingleaf was a calico whose ginger patches are a bit redder than usual), so if this doesn't technically count as unnatural, let me know. (yet another long comment go brrrr)