The yellow (buff) brick is ubiquitous in a swath from about Petrolia in the west, to Paris in the east. It's the defining characteristic of homes in many towns, including places like Glencoe or Woodstock where practically every building uses yellow brick.
London is a brick city, but brick houses are actually not that common in a lot of SW Ontario, except for the grandest homes. Most regular houses have wood siding. This is something in common with Michigan.
Typical 1.5 storey wood house of sw ontario.
Fancy wood house in sw ontario.