Deliberate mistake: Though it was, overall, far more historically accurate than most TV westerns, "High Chaparral" retained one anachronism throughout its run. For safety reasons, all the coal-oil lamps and lanterns on the set contained obvious electric light bulbs rather than burning wicks.
Deliberate mistake: At the end, the U.S. Cavalry "brand" Blue finds on the mule isn't a brand at all: it's obviously been applied with white paint to make it more visible to the camera. It's also unlikely that it would be so large, or that it would be located on the animal's neck instead of on its rump. (00:46:50)