The sample rules have some basic rules for coloring based on time. The important thing is learning how to use the different date attributes.
In your case, it seems you want to color by time since it was last worked on. I'm not sure what your definition of "worked on" is so I'm going to assume it's when it's accessed (you can change it to use Date Modified if you consider "worked on" to mean that the file was actually changed). You would also want to use date added for when you first add the file to the folder.
You would have probably have rules like the following:
"If date last accessed is not in the last 3 days AND date added is not in the last 3 days, move to trash"
"If date last accessed is not in the last 2 days AND date added is not in the last 2 days, set color to red"
"If date last accessed is not in the last day AND date added is not in the last day, set color to orange"
Ordering is important since the first rule that matches is the one that gets applied. Since files that are older than 2 days are also older than 1 day, you have the 2 day rule occur first so that it takes precedence. You could also add conditions to say "not in the last day but in the last 2 days" but this is more succinct.
Now, keep in mind Date Accessed is updated when you open it with an app. Just dragging it around will not update it (though dragging it out of the folder and back in will update the date added).
Try it out and let me know how it works out.