You cannot RNG on a retail disc for any GC game as the game's initial seed uses the GC/Wii internal clock, which is accurate to nanoseconds (1 billionth of a second). And of course the RNG abuse has literally just been discovered, and only able to be done on an emulator, and the key tool isn't going to be released publicly (damn hackers) so it would have to be done the hard way.
As for the shinyness it is still the standard 1/8192 rate for Colosseum but it will be unknown if it will be shiny or not until after the capture.
I have to go now as I have 8am classes in the morning.