When the developers sunset the previous tool, they were not able to migrate every single card in their database and as a result, some of the oldest ones (Hearth Gold / Soul Silver series, as well as Black and White) were not coded into Live
Eevee Grove : The latest release in the game, Eevee Grove is a strange set because it was thought to be the ultimate expansion for Eevee fans, but it doesn't include much love for the Evolution Pokemon beyond some new Eevee and Eeveelution cards and the new Penny Supporter and Eevee Bag Item cards
When Midnight Scavengers enters the battlefield, you may return target creature card with converted mana cost 3 or less from your graveyard to your hand
Beyond that, a good rule of thumb is that you should have a very good reason for adding an extra color to your deck: whether that's gaining access to a card that's particularly powerful, or shoring up a major weakness
Also suppose that our hand is largely filled with powerful, expensive six-drops