how to maintain sharpness while editing colors in Photoshop

[Najjar]

While selecting the wall avoid selecting hair. If there are too many loose strands, then you can try to cover them with ambient colors using patch tool or clone stamp tool. You can also try using alpha layers for more accuracy.

If the wall in background has a constant color all over without any change in pattern or color, one can also use Magic wand tool or try selecting the color range.

[Sheravat]

Editing a real photo requires more than changing color. One has to maintain the shadows and reflections of any object. If you are coloring the wall such that it affects the shadows and reflections on wall, it will obviously give sketchy effects.

[Don Of CS]

Once the desired object, in your case, try coloring it with brush set to hue mode. This maintains the shadows and reflections and also changes the desired color.