For that, there is a fairly simple tool to use, and while it doesn't require JPAN's Hacked Engine or (If I remember right), it does require a usage of an INI, and here's your tutorial:
http://www.pokecommunity.com/showthread.php?t=328270
DON'T use the OWE he provides in the tutorial, the OverWorld Editor Rebirth Edition works just fine. You can also just save the default BPRE INI sextion in another document and then switch out the two as needed.
And, if you want to know why you shouldn't use Pal 0 in any of your OverWorlds, it's due to the fact that one palette needed to be loadable without being overwritten (the one of the player), and, thus, if you do use Palette 0, your new OW's Palette will appear fine until you leave the area. The same thing happens with Palettes with a number any higher than 16. If you would like to use te player's palette, then just use Palette 16 as it is thenexact same thing.