No. You cannot get a gold Gyarados in any main series game, (not sure about spinoff games) as there is no way for a Gyarados to be gold. You can, however, get a gold Magikarp, as Magikarp's shiny form is gold colored. There is also a higher chance for you to get a shiny Magikarp by breeding the Gyarados that you can catch at the Lake of Rage, as that Gyarados is also shiny and, in Gen 2, because shininess was based off of IVs, you'd have a higher change to have a shiny Pokemon hatch from an egg produced by a shiny Pokemon.