I've never really thought about the color thing but I do know some cockers have smaller ear holes than others. Those usually are the ones who have the most problems.
First thing you need to to do is get them to a vet asap, to find out if the infection is yeast or not. Than you need to find out the proper way to clean there ears. Never never put any kind of drying powder in there ears, that only makes it worse.
When you do put cleaning solution in, after massaging the side of the ear gently to loosen the gunk, than take a paper towel or Kleenex on your finger and gently put in the ear to get rid of excess solution. They will shack the rest out.
Far as cleaner I buy mine from my vet but any of them work if they are used properly, don't use the powder items.
Also I cut off the top elastic of a sock, I put it on doggies after cleaning like a collar, than I tuck there ears into it on top of there heads. This allows air into the ears so they can dry.
Im not a expect but I am a life time Cocker Spaniel lover, I've had some with bad ears and some with good ears, im sure you know its a commitment and sometimes very frustrating but you can keep a handle on it once they see a vet to make sure you have antibiotic for the infection. Good Luck.
Christine and Patrick
Cocker Spaniels
Trevor and two Fosters Kahlua and Blossom
Life is What happens to you while your busy making plans.