Editing PNG Detached Instances

I have created email signatures and detached each instance as an exportable PNG. I now need to edit some font colors and a logo. Is that possible or do I have to recreated each signature from the master one by one?

Are you able to share a copy of the file you’re working from? Or maybe a screenshot?

Curious to know why you detached each of the instances vs using overrides?

I’m not a designer and doing this on my own from existing work I got. I have zero experience in Figma outside of what I was shown briefly. I have about 40 of these as PNG files and thinking I’m not able to edit any of them.