Gracias Shiny Ninetales =)
I knew you could not do it with GE. (A pity that Romi did not continue with the editor or if it had a version 0.06 or something and it seems that nobody is working in new editor, would have been great.)
Thanks Doggycharly I can easily change the world 1 palette.
But as for fixing hookbill's icon palette, changing the value of the offset BDE4F to [0C] a glitch appears in Level 1-1 icon.
I hope I have not done anything wrong, this error happens when I change the value  to [0C]