|: Stuff you'll need.
A) The ROM.
B) UnLZ-GBA. (Best tool evar.)
C) Paint/Sprite editing program. ||: Here's `Da fun
Open unLZ-GBA and load your Ruby ROM.
You'll have to wait while it loads the LZ77 Data.
Once done, goto 195, and pallete 53( I find it easier to edit, but you can use whatever).
Once thats done, click "Save image as...", then save it. KEEP UNLZ-GBA OPEN!!!
Open paint, and open the image.
First, you'll have to pick the background color and erase Latios/Latias, after you make a--Lets call it-- Pallete. Your new sprite your making can only use those colors.
After recoloring, you make the sprites lined up like Latios/Latias was.
Go back to UnLZ-GBA, and click "Import image...", or "import", or etc.
File --> Save ROM. Now you can check and see if what you put instead of Latios/Latias is there.
WHEWT WHEWT. It's there! You have edited your ROM intro thing!