It's not that unusual to occasionally find a Siberian retriever with eyes of different colors. (notinthedoghouse.com)
Waardenburg Syndrome Half Italian, half - Scottish forensic expert Enzo Macleod has distinctive good looks: long hair with a streak of white pulled back in a ponytail, and eyes of different colors. (bookbrowse.com)
The most likely cause of this, which Dr. Smith also mentioned, is complete heterchromia iridum — two eyes of different colors, one that is likely blue and hypo pigmented, resulting in a non-pigmented retina. (dogingtonpost.com)