at 10 weeks i say you have a pullet witch would explane her color
lemon cockoos have been breed to buff orpingtons and the result is buff hens and coockoo rosters because baring / coockoo geen in pure lemon coockoos the male birds have a dobel copy of the baring geen and both males and femals will show baring/coockoo but when you breed a lemon coockoo roo to a buff hen to make lemon coockoos only the roos show the baring because they only have 1 copy of the geen
the sad truth is most of the "lemon coockoo orpingtons "we have here in the USA are NOT PURE but are crossed with USA line buff orpingtons and this is why only the roos show the baring TRUE LEMON COOCKOO ORPINGTONS are dobel bared and both the roos and hens show baring like in anny other pure bared breed i hope this helps
BANJO