Has it been proved that Rayquaza is totally shiny locked? Or is the probability just very low?
In Omega Ruby and Alpha Sapphire, I'm pretty sure all legendaries are shiny locked, but in previous generations, they were not. So you can get a shiny Rayquaza and use it online and all, but it has to be from a previous generation.
P.S. I can give you a shiny Rayquaza for free if you like.
Hope I helped :)
Rayquaza is believed to be shiny locked.
According to the source, as it says "this is still under testing" I think it hasn't been 100% confirmed yet but there is a high chance it, along with Kyogre, Groudon and Deoxys, will be shiny locked.