As with most ducks, the females mallards  are not very colorful. They are light brown streaked with darker brown. This pattern is more apparent on the back than the belly. They have a characteristic dark eye stripe.

Both sexes have bright orange legs and violet blue wing patches, which are bordered by white bars on the leading and trailing edges. These wing patches are visible in flight.

Female Mallard
http://www.allaboutbirds.org/guide/Mallard/lifehistory