Basically you can change crystal's colour with almost any available element. Most can be done by making a hole inside crystal and place element in. For Fire and Spark, use Joint to prevent them from disappearing. Virus can be done through the infection process (But you need sth to hold the infected crystal) Ant is doable, but easy only at below 999 dots.
Also tried to make an invisible laser emitter with glass crystal. Probably usable as a deadly player-killer in player courses.