Thanks for your answer Dave!
I think I understand it more, but I need more experimentation to make sure I fully understand it. It's not about sending the byte directly to the WS2812 but interpreting that byte and sending a corresponding byte that the slave would interpret as a 1-bit or a 0-bit.
This makes sense to me, but then I'd need only two bytes instead of four. I still need to decipher the rest of the article.
Cheers,
Hoby.