The latter statement is incorrect, but it's an easy to make mistake. What he probably meant was that "in one tank, the vanadium releases electrons, turning from blue to yellow while in the other tank, vanadium accepts electrons, turning from yellow to blue."
The latter statement is incorrect, but it's an easy to make mistake. What he probably meant was that "in one tank, the vanadium releases electrons, turning from blue to yellow while in the other tank, vanadium accepts electrons, turning from yellow to blue."