Barred Rock pullets can be very dark or lighter than normal. Have had both, but usually they are darker than males. They do not always have a very dark wash and males can have some dark spotting on the leg fronts, too. BR sexing is not 100% accurate and some have conflicting traits.
Here's the kicker: if you're not sure of the breed, i.e. if it's a pure BR or not, you can have a dark male that looks very much like a BR pullet...for a few weeks, until that comb pops right up there. Case in point was some accidental crosses I hatched from a friend's BR flock. Her Silver Phoenix rooster got in a few good matings, unbeknownst to us, and I ended up with three or four SP/BR cross cockerels and one pullet. The males looked like BR pullets with ghosty barring and slightly longer tails, until the combs turned bright pink by four weeks old. The pullet was solid black.