@richiekhoo hmm mostly yellow, although if there's a lot of highling I'll use two additional colours to help with later review and referencing (e.g., purple to remind me of things Im catuious about and want to investigate/question further and orange for things I agree with that are particularly quotable).

Also, yes - Zotero is such a useful tool! I started using it for basic citation in academic contexts way back when and now it is my go-to for pdf reading across all contexts