Historical Rules · 19 January 2018
Rule 106.5
Official source text from the 19 January 2018 Rules release
If an ability would produce one or more mana of an undefined type, it produces no mana instead. Example: Meteor Crater has the ability “{T}: Choose a color of a permanent you control. Add one mana of that color to your mana pool.” If you control no colored permanents, activating Meteor Crater’s mana ability produces no mana.