Photoshop's Replace Color command is essentially a combination of Select Color Range and the Hue/Saturation adjustment. It allows a quick and interactive way to isolate and manipulate individual colored items in an image.
The first trick for using Replace Color effectively is choosing the right image to use it with. It works best for areas of medium coloration that contrasts with the surrounding area.
Start by using the Lasso tool to roughly outline the area to be affected. In this example, I'm going to change the color of this woman's shawl, so I have loosely outlined it. This will restrict the area that Replace Color affects.
Open the Replace Color dialog box (Image > Adjustments > Replace Color) and click on the middle eyedropper icon. It has a plus sign (+) next to it. Now when you click within the image it will add whatever color you click on to the replacement selection. Notice the preview thumbnail updating as you click. This is what it looks like after clicking on 5-10 different blue areas. In solid color areas you can simply click and drag to quickly select, but in this image black and white are interspersed with the blue, so we need to use several separate clicks to avoid adding those to our selection.
Fuzziness is how many values above and below the colors we clicked on to select. In this example, I've chosed 32, which means it will include colors that are plus or minus 32 in color value. For example, if we selected a color that was R100/G100/B100 it would include tones from R68/G68/B68 to R132/G132/B132. But I didn't do any mental math, I just watched the thumbnail update as I dragged the slider.
Once we've determined the selection to replace, you can change the color by dragging the Hue slider. Notice in my example part of the background behind her right shoulder is being inappropriately colorized. To eliminate this you'd simply select the minus (-) eyedropper and click on that area. You might need to then make some additional selection changes with the plus eyedropper and fuzziness setting. In fact, choosing an outlandish color is an excellent way to judge how accurate your selection is.
Notice that the area of color change in the image stops at the selection, but that the thumbnail preview shows the entire image.
You'll find some colors look more realistic as replacements than others, but dragging the Saturation slider can increase the acceptable options. The Lightness slider is less valuable, but can help in limited circumstances.