How do you get the Rainbow ticket after saying to helping Celilo find Ruby in Pokemon FireRed?

You actually don't get the Rainbow Ticket after helping Celilo find Ruby. The Rainbow Ticket is obtained in a different way, through a specific event that happens after you defeat the Elite Four.

Here's how to get the Rainbow Ticket:

1. Defeat the Elite Four and become the Champion: After you become the Champion of the Kanto region, go to the Indigo Plateau where you fought the Elite Four.

2. Talk to the Old Man: You'll find a man standing near the entrance of the plateau. Talk to him, and he will give you the Rainbow Ticket.

The Rainbow Ticket is a valuable item that allows you to trade any Pokemon you have in your party with another player, even if the Pokemon is not registered in the game's Pokedex. This is incredibly useful for obtaining rare Pokemon and completing your Pokedex.

Remember, you need to trade with another player who also has a Rainbow Ticket to use its special functionality.