I was raising two BLRW chicks - there are some photos of them in this thread https://www.backyardchickens.com/forum/viewtopic.php?id=226322 at 5 weeks and 9 weeks old... there wasn't a lot of difference at 9 weeks, but my hunch on which was which at that point turned out to be correct (1st BLRW was a roo, 2nd was a pullet). The major difference between those two was the size and colour of the wattles more than the comb.