There are many difference stories about the rainbow bridge.
The most well-known story, I guess, is in Norse mythology.
In Norse religion, a burning rainbow bridge called the Bifrost connects Midgard(earth) with Asgard, home of the gods. Bifrost can only be used by gods and those who are killed in battle. It is eventually shattered under the weight of war - the Ragnarok (German Götterdammerung). The notion that the rainbow bridge to heaven is attainable by only the good or virtuous, such as warriors and royalty, is a theme repeated often in world myths. Reference
You might meet the handsome Thor there.
Rainbow bridge is an improtant brief in Truku Tribe, a Taiwan Indigenous. Truku ancestors would tell the children, soul will certainly bridge Rainbow Bridge in. Where gains over the heads of men and the enemy will be weaving and knitting woman, a hand-washing blood out immediately. People like by Rainbow Bridge, where the ancestral spirits to enjoy life. Reference
If you are interested about this, Warriors of the Rainbow: Seediq Bale, a Taiwanese movie, might help.