A few yeast infection images I found:
Image by jon.hayes
Eleanor has developed "thrush": a yeast-infection of the mouth. We are treating it with a variety of methods including a bright purple dye called gentian violet. It stains her mouth and the aea around it. This is after it has been rubbed off for a while.
Image by Edinblur
This is my ‘summer lightning clone’ about 24 hours after pitching the yeast. The yeast froth protects the beer from infection. However, I still use a loosely fitted lid to keep dirt, dust and insects out (and probably cats too!)