What's the best way to do some basic CSS styling in Elgg 3, such as change some colors?

Read the docs.

are there any content card scraping plugins out there?

https://github.com/ColdTrick/oembed/releases

I’m remembering why I got rid of Elgg and tried something else. Such a helpful community here. Wow.

I already have oembed- I was asking about a scraper. I think it’s safe to say one doesn’t exist.

I’ll continue reading the docs or just find something else again that makes CSS editing more straightforward.