Here is a quick little tip that can save you hours and hours of color matching in photoshop. Surprisingly, it does not involve reviewing real colors and matching them. Digital artist Antti Karppinen just sent us this tip, and I wish I knew this year ago, it would have saved me so much time trying to match colors of various objects in photoshop.  Antti tells DIYP how the magic works:

I use this technique to match the tones of images that I’m going to composite together.  This technique “changes the colors” so it’s easy to see any mismatches in color. This makes it easy to tweak them  It’s all done with some special layers. 

The first layer is a neutral gray layer in luminosity blending mode. This gives me a color map and I just push the saturation adjustment layer to +100 to see the color map better. Then I use the selective color sliders (black, neutrals, white) to tweak the colors and looking at the color map to adjust the images to blend together.  You can also use color balance to do this, but I like the control that selective color adjustment layer gives me. Here is a further breakdown. start with two photos that don’t match (brownish on the background, blueish on the model).

To break it down further, the first step would be to create a neutral gray layer, and set the layer blending mode to Luminosity. This will create a color map.

The next step is to add a hue/saturation layer to help bring out the color differences between the two layers. Slide the saturation all the ways to the top.

Now create a selective color layer and link it to one of the composites images. Use the sliders to match the “false colors” on the two images.

Now the images match:

[Best composite image technique to match tones | Antti Karppinen]