The rainbow contact lenses belong to the colored contact lenses which can be used to make your eyes look special and beautiful. On Halloween, a lot of people try on this type which may make you look personalized. However, if you keep the good habit of hygiene, wearing this type of contact lenses is safe.
Well, actually, I also find the type of contacts you described really interesting, and it is becoming a trend recently. Basically speaking, wearing such kind of contact lenses would not cause direct harm to your eye health however, you should not ignore the fact that there are always consequences which could turn out to be disatrous. And it is really not to wear them all the time right? So, you gotta outweigh the benefits and risks.