HueShifter is an amazing new application for doing color transposition or "color shifting" in images. Unlike other graphics applications, HueShifter works in perceptually uniform colorspace so you can make changes that are virtually imperceptible, all while working with color dimensions that you're familiar with - hue, saturation and lightness.
HueShifter works right alongside Adobe Photoshop and many other image editing applications. It supports Drag & Drop and Copy & Paste, so it's easy to get image data in and out. Drag or paste images into HueShifter, then drag or copy the results back to another app. Or use HueShifter's selections to make a grayscale mask for use as a layer mask in another app. Plus, HueShifter supports images with alpha and it maintains embedded color profiles so your colors remain accurate.