It may or may not be the case here but when you see a male's blue cere begin to turn brown, sometimes referred to as feminizing, it can be an indication of a testicular tumor. The tumor will produce female hormones causing the cere to turn brownish, similar to when a hen is in breeding condition, sometimes a Lupron injection can help curb the hormones.Never seen anything like this. I can't tell if it's some type of dried discharge or if the cere is actually changing colors. Is trying to clean it an option to see? If this is something that may happen to males, I'm interested in learning what to do about it as well.