Greetings,
The description of your project is a little confusing. By this I refer to "illustrator PDFs". Does that mean you have the Illustrator files, only saved as PDF, or do you have the actual Illustrator .ai files?
Granted, a PDF can be opened in Illustrator without issue. The layering will not be the same as the native file, yet, it can work.
Item 1: Creating an action to change the color will work well if the spot that the color(s) are used are solid fills. It won't work if you have items that use the color in a blend.
Item 2: Placing the "image", which I assume to be the original file that has the color changed, into another Illustrator file cannot be automated. Well, it can, but, it may not be in the best position in the second file. By this, I am referring to how something is "duplicated" from one file to the next. Yes, duplicating can be done from the layers panel, but, the second file must be open and the layer where the "image" is to be placed must be selected. Otherwise, the new layer will be the layer that was previously selected in the second file.
Questions: will the "image" need sizing or moving in the second file? Do both files have the same dimensions? The original filename is referred to in Item 2... are the files to be saved as PDF or .ai ?
I'm more than willing to discuss this, yet, from first glance, the project will require a bit more work on item 2.
Let me know how I can help and if you have any questions.
Thanks,
Marc