Why the emphasis on the color silver? For the same reason RWBY also emphasized "silver eyes"; it's a reference to The Wizard of Oz, where the slippers were ruby-colored in the film but were silver-colored in the source material.
Likewise, silver is used in both RWBY and SLVR because of how it is the weakness of various fairytale creatures (such as werewolves — and Lycan is a wolf faunus...).
In alchemy, silver is one of the seven metals and is associated with the moon. Hence the series' alchemy motif as well as Team SLVR's moon motif.
The Philosopher's Stone is believed to be the key to transmuting base metals (common, inexpensive metals) into precious metals — gold and silver.
Also going with SLVR's alchemy theme and connection to RWBY, transmuting prima materia (i.e. the starting ingredients/materials) into the Philosopher's Stone via the process of magnum opus has four stages: nigredo (blackening), albedo (whitening), citrinitas (yellowing), and rubedo (reddening).
