Possible meanings are 1) the shields appear red as the light from the sun reflects upon their metal surfaces or 2) the shields are covered with leather that has been dyed red.
This likely refers to the light from the sun reflecting upon the metal chariots.
# on the day that they are made ready
This can be stated in active form. AT: "when the soldiers have made them ready" or "when the soldiers have prepared them to attack" (See: [[rc://en/ta/man/translate/figs-activepassive]])
# the cypress spears are waved in the air
This can be stated in active form. AT: "the soldiers wave their cypress spears in the air" (See: [[rc://en/ta/man/translate/figs-activepassive]])