Both of the pictures above are of my chihuahua's left ear. She would not allow me to get a picture of her right ear, but it looks more red. Her ears are sensitive to the touch (she hates when they are touched; she jerks her head away.) Already posted asking what kind of infection she had, but thought I would add some pics. Going to take her to a vet on Tuesday probably.
Vet will be your best bet. They will be able to look under a microscope to see if it is an infection, yeast, or mites. There's also the "sniff" test vets are rather good at and you just can't do that over the Internet! :-D