Well you can change which palette slot its loaded into by doing some HEX editing. The best way to go about doing it is to use the old version of NSE and open up its in-built HEX editor (Ctrl + H). Open the empty drop down menu and select 'Sprite Offset'. From there onwards you're going to need to know how the OW data is structured - JPAN's hacked engine explanation guide has a good table that shows it all. Find the byte which determines 'Palette slot +???' in JPAN's guide as that will change where that palette is loaded.
Hopefully that's a good enough explanation :P
Hopefully that's a good enough explanation :P