Your pictures show that the rubber seal is not clean, so you might clean those, too. Same tip with water or IPA, slightly moist microfiber, just to clean that "goo" from the rubber seal around the edge of the display.
As the "stain" is simply on the aluminum surface, you might try something that might move that "stain" off, such as small amounts of "WD-40" or "3-n-1" oil to moisten a paper towel, or similar, then wipe through the stain. Be careful not to get any liquid into the speaker openings, as you will be right on the edge of those. Also, don't touch the keycaps, and, of course, never the display screen. First test a more visible area, such as where the stain curves near the back left or right corners. You should be able to see right away if that helps or not.