Step 3: Add A Solid Color Fill Layer Below The New Layer

Now that we have the main subject on its own layer, we're going to hide the background from view and replace it with a solid color. First, click on the Background layer to select it. Then, with the Background layer selected, click on the New Fill Or Adjustment Layer icon at the bottom of the Layers palette:

We want a solid color behind the main subject, so select Solid Color from the top of the list that appears:

This brings up Photoshop's Color Picker. Go ahead and choose any color you want right now for the background. It doesn't matter which color you pick because, as we'll see later, you can always go back and choose a different color any time you want. I'm going to choose a light blue for now:

Click OK when you've chosen a color to exit out of the Color Picker. Here's my image with my solid colored background:

And I can now see in my Layers palette that I have a solid color fill layer between my Background layer and the "threshold" layer: