Uhm. I only know how to do FE7 one, but if it's not that different...
Check your rom with that map in nightmare under... chapter data editor.
Change the, IF it's identical as fe7 one, second to fifth(?).
They're coded to the map's palette that you chose.
But I doubts that as the map of your and chapter 2 is identical, so it's likely an error else where.
But try it anyway.