Custom Themes & Variants

I'm working on creating a variant of my company's existing theme and need to modify some colors and fonts.

My question: Are there any guides or tools that show everywhere a specific element (like a particular color or font) is being used throughout the theme?

I want to make sure when I change something, I can verify it looks correct in all the places it appears. I need to be confident that my variant will work properly across the entire application before implementing it. Any documentation or best practices for theme testing would be really helpful!

Thanks in advance!