Delta is the difference, for each color, between the current supply of USDV and the quantity of USDV originally minted. For example, if USDV_BLUE started with $100 tokens minted, but $50 were recolored to USDV_RED, Delta_USDV_BLUE= -50 and Delta_USDV_RED = +50.
Delta can also be thought of as yield potential, or how much the current vault shares of a given color may change in the near future. A positive delta (surplus) means there exists potential yield that is not being collected. A negative delta (deficit) means there is the potential for yield reduction.
Delta is calculated separately for every color on every blockchain. Verified Minters choose when to remint based on their color's delta value on each blockchain.
Volume vs TVL
A Verified Minter's delta can never fall below its TVL (See ColorTrace Safety mint-holding guarantee). However, a Verified Minter can gain vault shares beyond its TVL by recoloring USDV that flows through its contracts (See Remint).