Using the Colors AlTaglio you can tweak the color palette of your photos using gamut masks. This method of creating harmonic color schemes is used by artists all over the world and until now has never been available for photo processing to the general public.
Change the hue, not the luminance.
Since Colors AlTaglio works in a CIELUV derived color space it can make sure that the perceptual luminance of each pixel is preserved through every edit as it only modifies the hue and saturation components.
Rotate the color wheel.
Besides transforming the mask you can also rotate the color wheel to offset all the hues at once. Rotate it a little bit for a subtle change in temperature, or apply a large rotation for a trippy color scheme!
AlTaglio provides an extension that enables the standard iOS Photos app to use all its functionality without leaving the Photos app itself.