Peafowl, is it only the males that have colorful feathers?

Question

I thought the hens were brown..can they be green or blue also?

Answer 1

Yes. As in most bird species, hens are dull colored to help them avoid detection of predators while incubating eggs on a nest.
Some exceptions are hole nesters such as woodpeckers and some of the (very few) species in which parental role reversal occurs such as the phalaropes (where the female is promiscous and lays several clutshes of which are incubated by the males without help from the females which perform the courting display)

Answer 2

There can be color variations in females (peahens) but like a lot of the avian species the male is much more colorful then the female. It is a trait developed so the male can attract mates and the females remain well camouflaged to protect them and their brood.
peafowl are probably the most obvious example but Mallard ducks, Cardinals and most song birds exhibit this characteristic