Changing transparent background.

Hello all,

When I choose create a new fill or adjustment layer to change the background color, the color is gray in the background and will not change to the color I chose. There must be a setting I accidentally turned on or off for this to happen. Here is the video I am learning on. The part that I'm unaware of is at 20:00 minutes. My color changes from transparent to gray. The color won't change to teal as in the video. Any suggestions? Thank you. 
Wrt