Image App
Personally, I’m a huge fan of “Do one thing well,” rather than a Leatherman Tool approach. A folding set of pliers that is a wrench, a screw driver, a diagonal wire cutter, file, saw, punch, one too-many uses?
That being noted, about the only tool I keep on hand, at all, is a vintage Leatherman, an original multi-use tool.
Instead of making this complicated, it’s a simple app that manipulates images, just one way.
While this is certainly possible in PhotoShop, there’s a single app, I just toy with it on the iPad, and the app does one thing: colorize.
Color App
That’s not quite it, what the app does? It turns a digital image into a black and white, more like a grey-scale shot, then has a variety of brushes that renders the original color.