Is there a way to change the standard yellow color of folder icons (including thumbnail view)?
Go to Preferences / Favorites and Recent / Labels and click the Add button:
Call the label "Red Icon" or whatever you'd like, and use the Icon Color selector on the right to specify how you want the icons to be re-colored:
Then go to Preferences / Favorites and Recent / Label Assignments and click the button to Create a new wildcard label:
Set it up to match all folders and use the label you created ("Red Icon" in my case), like this:
Then click OK in the Preferences dialog.
Thanks!