Two ways
By Luck
Action replay
red gyrados is just shiney gyrados use the shiney code and find gyrados
The red Gyrados is found in the Sendoff lake at the Spring Path.
to get a red gyrados you have 1% of finding a red gyrados and you have to use a super rod to find a red gyrados.
The Red Gyrados drops it. If you already fought the Red Gyrados, you should already find it.
The red qyrados is just a shiny grados and u can get gyrados when fishing with a good/super fishing rod imn Sinnoh
at the lake of rage
use pokeradar on a body of water that has lots of gyrados
Actually there is no red Gyrados. I mean there is, but a red Gyrados is a shiny Gyrados.
red gyrados is actually a 'shiny' gyrados, meaing it's just a weird thing that the Pokemon games have were every couple 10,000 Pokemon or so. so in order to obtain a red gyrados you would have to go through quite a lot of finding a shiny gryados or shiny magikarp(if you evolve taht it should stay shiny)
beating / catching the red gyrados in the lake
Gyrados's shiny color is red so if you ever find a shiny gyrados or magikarp catch it. Also at the lake of rage you can catch one that is already red.
you find a red gyrados at the rage lake