Delaboratory

Delaboratory is a tool to adjust the color and contrast of your pictures in a really easy way and without permanently altering the image file.

The application lets you work with up to nine color spaces (RGB, BW, CMYK, CMY, LAB, LCH, XYZ, HSL, and HSV), as well as layers, a color curve, a channel mixer, and other parameters.

Delaboratory is a simple tool that does it job perfectly well, although it doesn't include all the same features that more sophisticated applications have.