I think the OP_RETURNs of the transactions had different color codes in it. To make the image
Still, there must have been some serious forethought put into making this happen.
Kudos to whoever engineered it. I'm impressed.
I tried to capture a screenshot of it using archive.today, and archive.org, but was not able to get either of those services to accurately capture a screenshot. So I snapped one myself, just in case mempool.space changes their code in such a way that it doesn't display it the same way anymore: https://i.nostr.build/aQ3JZ.png
Notice the # of transactions in that block. I think that's a new record for bitcoin.