White dogs can be challenging to edit, especially when they have the dark stains around their eyes or muzzle. As with everything in Photoshop, there are a variety of possible solutions from selective color replacement, selecting a certain color range, painting, and changing the blending mode, or just click this FREE action.
I created the action by making hue/saturation adjustment layer and adjusting the saturation of the colors of the stains and adding a bit of luminance. Follow that up with a mask and simply paint in where you want the adjustment. You can download that action, and my sparkly eye action below.
One other common challenge that I address in this video is my super simple way to blend the background when content aware or patching just doesn't do the job. Photoshop does the spot healing tools extremely well, but has a tough time on really soft or gradient backgrounds. For those backgrounds, the clone stamp and a mask are my best friends.