I go for GREEN
when ever possible on the Mallrds. Yes I do make a mistake occasionally by misleading and hit a hen. I guess my point is I aviod hens is my philosophy. And not just Mallards, but other easily identifable species like Cans, Reds, Ringers and Blue bills.
Up here they are in eclipse feathers at start of season, so hard to ID and hen from a drake, but by end of Oct, generally they are fairly easy to tell the difference.
Up in CA in end of Sept it can be a reach bitch to tell them apart--remember the young are born 2 to 3 weeks later than in S MN or SD, so much less fledged out.
Also for the Northern tier hunters---when a lone hen comes in, pass on it. Often it is a recooperating hen from the riggors of raising the ducklings, these "skilled" hens have the best chance for pulling off a brood the next year, so please pass of them. Remember the the #1 mortality of hen Mallards is from predators, March-June when they are on the nest. So give them a break.