The most popular selective coloring app on Mac App Store
ColorStrokes is the most popular and feature rich selective coloring photo editor on Mac App Store. It was released in 2011 and is ahead of any similar image editor since then. You get tons of artistic tools for hassle-free color splashing, including possibility to apply custom colors, change background to sepia, separately enhance background and foreground, tweak hues, add blur, vignette, dramatic effects and more.
ColorStrokes was originally created for Mac OS and is now also available for iPhone and iPad.