Wiley,
This is the thing about recessive genes, with silver in particular, you could have a loft full of blue and blue cheq cocks, and every one of them could be carrying that dilute gene, therefore having the potential to produce silvers and silver cheqs. Chances are that some will be produced, but it is equally feasible that none may be produced. Point is, as that strain progresses, the recessive is carried along with it, but the gene pool shrinks as the better performers are selected, so all the time there is more chance of the recessives surfacing.