How do I create a transparent box with only the colored border visible

If you want more control you could use the Rectangle Tool and either add a stroke with layer styles or turn down the opacity

and then you can move, resize or change the color at any time.

Highlight:

1. Draw the retangle, double click on the shape layer in the layers panel to choose the color and then lower the layer opacity to taste.

    You can use the move tool to reposition the box or resize by clicking on one of the corner handles.

Stroke:

1. Draw out the rectangle.

2. In the effects panel under Layer Styles choose Visibility and Hide

    (the rectangle color will diappear)

3. Go to Layer>Layer Style>Style Settings and choose Stroke in the dialog.

   (you can choose the color and size of the stroke in the dialog)

MTSTUNER