I have 18 pullets and 2 cockerels. Two are RIR pullets and two are Buckeyes. For the life of me, I can't tell the difference, even though I've googled, read and even gone to the local farmer supply store. Right now they are are two days shy of being 12 weeks of age. I spend a lot of time with them especially cause I allow them free range time and I have to keep them safe from eagles/hawks and adult hens , so right now they are the same color, size and yellow footed. Attaching a picture of one of them.