This is a good idea, but it appears there is some color bug (or intention) showing red color instead of green for almost empty blocks.
I know this is only visual and it's not a big deal, but I saw something strange and compared it with main mempool.space website.
You can see this in screenshots posted below:

It's intentional. I think OrangeFren decided to use two completely different color themes, while mempool.space just used different shades of green to represent the zones. According to my understanding, the transactions in the "unconfirmed blocks" or mempool are divided into two. Those that have a fee rate of 1 sat/vbyte and above represented by green, and those that have a fee rate of less than 1 sat/vbyte to zero represented by Red.
You're right about the colours, but it wasn't intentional. This is a bug from the latest release of mempool.space and the official instance fixed it. We could fix it too, but it does fit quite well, because most nodes and miners won't accept <1sat/vB txs, so they are a bit risky to rely on.
That said, we made sure our node is connected to other <1sat/vB nodes, so if you want to broadcast such a tx you can do so here:
https://mempool.orangefren.com/tx/push and it ought to reach the miners that accept such txs.