Canvas extension color greyed out in the Canvas Size dialog box?

I am trying to put a border around my photo in Photoshop using the Canvas Size tool. In the dialog box at the bottom my Canvas extension color selection is greyed out (no available). How can I fix this. I am using photoshop CC and the latest update.
I have searched around and can not find a fix for this.
HELP

Maybe your Background layer is a smart object?

Change the bottom image layer to a background: Layer > New > Background from layer. A little padlock icon will appear, showing that it is a background layer. Now you can set the color in the canvas size dialog.

Thank you Peano,
You nailed the problem.

Guntoter