You can catch red Gyarados anywhere because red Gyarados are only shiny but are extremely rare.
same chance to catch a shiny gyarados to catch eny shiny in platinum.
Yes, the "Red Gyarados" is actually just a shiny Gyarados.
train it
To get a red Gyarados in Pokemon LeafGreen you first need to catch a shiny Magikarp. This shiny Magikarp will be able to evolve into a red Gyarados. This is due to the red Gyarados simply being the shiny color of Gyarados.
In Pokemon Crystal version, you catch it at the Lake of Rage.
GYARADOS
Catch a shiny magikarp and evolve it.
the only way to get a red gyarados is to find one already shiny in the wild. you dont get it from someone in the game either.
A red gyarados is a shiny gyarados (however, the Pokemon Company did not call them shiny untill the Unova Region). You can find it wherever you can find a normal gyarados, but your chances to find it are very slim.
A red gyarados is just a shiny gyarados, it will still take time to accomplish.
Red gyarados is actually a shiny pokemon so you would have to catch a shiny magicarp and evolve it in a shiny gyarados (meaning a Red gyarados)
you need to catch a gold magikarp(shiny) by fishing or breeding then level it to 20. Or you can catch a red gyarados(shiny) by random. The chance to have it red are i in about 8000