To do this, you need an acro bike. Set two of your pokemon that you want to raise in the daycare to the left of Mauville. Now go to a sandy slope at the top of the desert area (make sure you're facing the slope). Then place a somewhat heavy object (like a glass cup) on the up arrow of the gameboy, make sure you balance the object up against something so it doesn't fall over.*HINT*if you have one of those things that plug your gameboy into a wall, it would be preferable so the battery won't die down overnight.
There is an incredibly small chance of a pokemon in a different color. 1 in 8,192. I caught a pink mawile long ago when the game came out. However, you'll probably wind up findin' a shiny lati@s 'cause 1 out a 600 is them unless you caught a regular one, found a regular one, killed it, etc. ****NEVER ATTACK THEM CUTIES**ESPECIALLY LATIAS*****MY NAME IS NEONLATIAS******** >-> I am warning you...
Go to freewebs.com/wiirockers for all the best pokemon stuff. see yah there