You should now see a colored outline around the outer edges of your mask by those marching ants. Click control (or command) D to deselect the mask. I wanted to add some visual interest, so instead of leaving the stroke lined up exactly with the outside of the shape, I grabbed the move tool. Then I clicked on the outline, and then used the arrow keys on my keyboard to offset the stroke slightly to the right.
I hope you enjoyed this tutorial, and if you want to pick up the gorgeous kit I used here, it's the FocusClickRepeat Collab kit by Celeste and Amanda Yi. Have fun with this technique have a beautiful day!