What is red BTC?

Excuse me, could you please clarify what exactly is meant by the term "red BTC"? I've come across it a few times in discussions about cryptocurrencies but haven't quite understood its significance or what sets it apart from regular Bitcoin. Is it a specific type of Bitcoin, a fork, or something else entirely? And if it's a unique variant, what are the key differences between red BTC and the standard Bitcoin that we're all familiar with? I'd appreciate any insights you could offer to help me better grasp this concept.