User blog comment:Guidorz/Jokers Ruling/@comment-39646902-20190531131427

its one of the basic rules to the duel masters game. when your using your mana, at least 1 card needs to provide the colour of the card you are using. for eg,  when you cast a water/light spell that has 5 mana cost, you need 5 mana. at least 1 needs to be a water and 1 needs to be a light. the rest can be from any colour mana.