Leaf is an unusual graphics tool which converts an image to greyscale, sepia or a negative view, then allows you to selectively paint areas back to their original colour.
If this sounds odd, the key is the word "selectively". Imagine a great portrait shot of someone, converted to greyscale, where you've restored only their piercing blue eyes. Or a view of the countryside, now in sepia, where just a single tree has been returned to its original green. With just a little imagination this technique really can produce some stunning images.
Leaf ensures they're easy to achieve, too. Just drag and drop an image onto the program, choose your brush size and start painting. And as you drag the brush over the image the original colour is restored.
The program doesn't include a zoom, unfortunately, which can make fine work rather a challenge. And there's only one brush; a circle. Still, there's an Undo option if you make a mistake, and when you're happy the results can be saved as JPG, BMP, PNG, GIF, and even PDF files, all in a click or two.