TCG Design - Why is 5 colours so common?

There's plenty of possibilities when designing a colour system for a tcg. So why do so many games use the same 5 colours? There are some obvious and some not so obvious reasons this is such a common standard.

Merry Christmas! Actually, the timing was a coincidence. This will probably be the last scripted video for the year, but I'm going to try getting a live stream going next weekend - hopefully it'll be listed on Thursday-ish? Still need to confirm a few things, so it's still not 100% - but I've been looking forward to it for a while, so fingers crossed for no issues! Thanks for sticking around with me for 2023!