Yes, Several Pokemon such as Pikachu, Gengar, Raichu, Dragonite, and more all have rainbow variants representing the Gigantamax abilities that they have in Pokemon Sword and Shield. All of these variants are powerful and armed with lots of health and very interesting abilities. Whether you are collecting the rainbow pokemon or end up getting lucky and finding one in a booster pack, make sure to keep it and try to find the V version as well. It can be a massive boost to your team and your deck as a whole to keep these Pokemon around!