If so, it could be that he was wearing blue shirts long before he started working for the Cannon family.
From the opening scene of the 'Bonanza' episode "The Mission", Hoy can be seen as a cowboy drinking at the saloon in town where he had been listening to the stories of old Charlie Trent. When a couple of other cowboys started roughing up Charlie for what they thought were lies about his connection to the 1847 Fremont Expedition, Hoss Cartwright had to step in to save the old-timer.
Hoy played about nine roles in episodes of 'Bonanza', and we're not making the claim that all of them were Joe Butler; just this one. As for the rest, since the simplest splainin is always the best, we're going to claim that Butler's Pappy was a rolling stone......
A 'Bonanza' website timeline established that each episode took place 100 years before it aired, so this would be taking place around 1860. And as a Calvary captain (played by John Dehner) pointed out, there looked to be a war coming, so that could be verification.
Now, at a website celebrating 'The High Chapparal', it was voted that 1873 was the year in which the High Chaparral ranch was founded. So that gave Joe Butler plenty of time to grow that mustache of his.... BCnU!