Other than Slivers, from the get go they were meant to be all colors, and were very, very popular as a result
Bellos trigger only affects non-Equipment Artifacts and non-Aura Enchantments that cost 4 Mana or more, which means its better to have a few of those down before Bello actually becomes useful
This one mana cheaper, Dimir color identity Fortunes Favor will probably find its way into some of my decks
For example, if you control Arcee, Acrobatic Coupe and March of the Machines, Arcee will be a 2/2 artifact creature during your turn and a 3/3 artifact creature (because its mana value is 3) during each opponent's turn
Its an 8-mana sorcery that gains you 2 life for each card in your graveyard, then shuffles your graveyard into your library