Jayburd wrote:hybrid BC/RCs have an intermediate sitting position. You'll notice blue caps always sit almost vertical on the perch, especially males. Red cheeks more horizontal. Intergrades in between.

Wow, thanks for that bit of information! I ran right out and watched a cage of male BCCBs, with one male RCCB included, and there is a definite difference in sitting position--never noticed! Of course, I am not the most observant person anyway.

I have a cage of hens, BCCB with one RCCB, and later today, I'll watch them and see if I can pick out the RCCB hen without looking at her leg bands. Also check the four hybrids I have. The male hybrids are very easy to spot, they have cheek patches that are only half the size they should be, so they stand out, at least for me.
Lea, I know you don't want to hear this after searching for Cordon Bleus for a year, but if you have two RCCB males and one BCCB hen, the best thing would be to try to find an RCCB male and two BCCB hens, if you can. If you pair this hen with one of those males, you will get fertile hybrids, which dilute the pure bloodlines when they are mated with pure mates.