Here in Sweden, blue and black are the most common colours among show cockers. When it comes to working cockers, liver seems to be most common, although this is based upon my experience not statistics. I have seen liver, golden (red with brown pigment), black, liver roan, liver and white and blue roan working cockers. I do not thing there are any sables among working cockers.
Then - among show cockers - the most POPULAR colour seem to be anything but blue roan! Since I plan to breed from my bitches (both blues) and am NOT going to have colour as one of the things that will be taken into consideration when I choose sires, I am a bit concerned about how 'important' colour seem to be for many persons who are interested in the breed. One could think that temperament, type and how well the dogs have done in the ring or in other doggy activities would be more important, but in the majority of cases this does not seem to be the fact.
If you breed livers, sables, black & tans or any other 'rare' or popular colour, you seem to have much more interest in the combination no matter the merits or health stats of the parents. One can understand that breeders sometimes prefer to mate their bitch to a dog of popular colour and not as good record compared to one of common colour and better merits.
I myself have never had anything but blue roans, but it is beacause that the dogs that have come my way all have happened to be blues. Of course I would like to have something different one day - mabye a red (my favourite colour), or an orange or a black. But still, I do think that colour is something that will make a GOOD dog a tiny bit better - it is a bonus. I will never make a bad dog good!