he's probably deaf on the side of the blue one.
edit: damn i was wrong!
There is a common misconception that all odd-eyed cats are born deaf in one ear. This is not true, as about 60%–70% of odd-eyed cats can hear.
[4] About 10%–20% of normal-eyed cats are born deaf or become deaf as part of the feline aging process.
[4] White cats with one or two blue eyes do, however, have a higher incidence of
genetic deafness, with the white gene occasionally causing the
degeneration of the
cochlea, beginning a few days after birth.
[13] See also
deafness in white cats.