[casthaven]Entreat the Angels[/casthaven]
Thats especially true because Delighted Halfling can also be tapped for one mana of any colour, as long as that mana is being used to cast a legendary spell
The deck features enter the battlefield triggers including graveyard hate (Angel of Finality), Bolster (Anafenza), artifact/enchantment removal (Angel of the Ruins), creature tokens (Blade Splicer, Emeria Angel, Regal Caracal), flicker (Charming Prince, Restoration Angel, Flickerwisp), reanimate (Emeria Shepherd, Karmic Guide, Sun Titan), venture (Nadaar, Radiant Solar), fetch (Solemn Simulacrum, Ambitious Farmhand), creature removal, life gain, and much much more
How it works, what set it debuted in, if its evergreen, and what the best cards are featuring it, answers to some complex rules questions, and more
Rather than talk about specific cards I am just going to list the good and appropriate stuff for each of the three options and talk about what that colour does for the archetype