Grow v. KeepThere are two different versions of how the borders will interact with your image.
A border is placed around your original image size increasing the image size.
The original image size is reduced to allow room for the border, keeping the image size the same as before the border action was run.
Understanding Border LayersGroup Layer
This layer is like a little bucket of your image and border layers. You can drag this group layer onto an album design layout and as long as the Color Fill layer (4.) is turned off (no little eyeball on the left), you will match the background of the page to the background of the border.
Color Fill Layer
Double-click on the icon that looks like it has a white box with a see-saw below it. If you click in this area it will bring up your color picker and allow you to choose the color of the outside border. Remember you can play the "Invert Border Color" action to invert the colors. Turn off the little left hand eyeball and then drag your group layer to an album layout to use a bordered image without the exterior frame.