This patch applies a small ASM hack that enables a custom palette (by default on palette 8, which is used by the 'Nintendo Presents' logo). The background colour can also be changed. You have to change the RGB values of the custom palette yourself (by default they're all FFFF, which is white).
No credit needed.
I'm the one who upgraded the patch to Asar and SA-1 and I decided to look into DiscoTheBat's comment.
The patch hijacks $0093D7. A little before that (at $0093CA) is code to reset the screen brightness and mosaic. The game jumps there two times: at $0096AB and at $009756. I'm not sure about the second jump, but the first one happens during the Mario Start! screen, making the check for OnlyNinPre required.
This patch is a very simple way of changing custom palettes for the nintendo presents object and I really like that concept.
Nevertheless, I debugged the code and it seemed that the codes from Main and Return aren't really needed, meaning you could jump straight to the OnlyNinPre. Also, you should try to use JML instead of JSL for saving time. But it is a pretty good patch, so, good work!