I would suggest different colors than black and blue. I found myself not able to differentiate unless I tilted my laptop monitor away. I can't imagine that color blind users would have a better time. May I suggest red and black?
Blocky is great! The maintainers are also really easy to get along with. I had a few features I needed to get off of pihole (cnames, defining DNS via zone files) and they worked with me to plan the feature and were very kind and responsive with reviews of my pull requests :)
Oh, and if you do stick with react, I'd suggest this library! It's super powerful. I'm using it for some visualizations at work and it's pretty awesome what can be done. https://recharts.org/en-US/
I kind of doubt it, but you could fake a realtime api by streaming results from your backend of choice as if you were getting it from an api. Some of the data is large enough that you could download it async on your backend and stream results as you parse it! I'm actually downloading the liquor sales for my state since 2012 and so far it's over 2gb of data, so definitely stream-worthy.
I'm not sure if you're in the US, but there are a lot of data sources at https://data.gov/ that are pretty interesting! A similar service may be available for other countries.
If you want to really get out of your comfort zone, I would suggest a new language/paradigm. I've recently been loving learning Elixir with Phoenix liveview. It fills a lot of the full-stack needs and lets you focus on your backend data and your frontend display.