Making custom highlights for a menu can be done in Photoshop and basic directions are in the manual. It is all done in the GUI of DSP and is relatively easy.
The best way to do this would to use the background and overlay method.
The background contains everything for the menu except the areas/shapes to be highlighted(tif or pct-no layers).
For one color highlights the overlay layer would have a white background with black to denote any areas/shapes that DSP should read as the area you want to change to the selected highlight color when the button is selected or activated.
There is also a method for doing your menu with a layered photoshop file.
I would not recommend this as you menus will run slow and could lead the user to believe the DVD isn't working properly.