I find different eye colors in dogs fascinating. This little Shih Tzu has such different eye colors and such an intense gaze that I spend an entire afternoon taking photos of him from every angle.
Two different eye colors in dogs is actually rather common and often found in Siberian Huskies. Melanin is responsible for the amount of pigment found in eye color. Blue eye have no melanin and brown eyes have a lot in an area called stroma.
Having two different eye colors does not cause any problems for the dog other than receiving even more attention than usual. :)