It means it is shiny
Actually there is no red Gyrados. I mean there is, but a red Gyrados is a shiny Gyrados.
They don't mean anything at all. Just for decoration.
Get pokemon red
No. They are not.
What is a red chain?
You can't get the Pokemon in Pokemon Platinum.
migrate it from Pokemon fire red version
Of course
action replay
No
yes
you see all the Pokemon in platinum and trade from your other games like emerald, blue, fire red etc and that is how you find all Pokemon in platinum.