How do I tag folders and subfolders

Right Arrow will expand the selected folder in list view :

& Left Arrow, will close the selected folder.

Option + Right Arrow will expand the selected parent folder, & all sub-folders.

Option + Left Arrow will close the selected parent folder, & all sub-folders.

Selecting all, Option + Right Arrow, will expand all the folders, & sub-folders.

Selecting all, Option + Left Arrow, will close all the folders, & sub-folders.

Here is another solution that creates an Automator application. You can assign one label color to the entire folder hierarchy, or one color for the outer folder, and a different color for its sub-folders and files. Or, you can simply run the application, select the outer folder name, and then apply None ( x ) for both label color prompts, and remove all label colors for the outer folder and its contents.

1. Prompts for the folder to apply or remove folder labels too

   Prompts for the label color (or X for None) to be set on the outer, selected Folder

2. Gets a list of sub-folders and their contents

   Prompts for label color to apply (or X remove) on the sub-folder hierarchy

Launch Automator (Launchpad : Other : Automator).

1. New Document : Application : Choose.
2. Drag/drop the following Library : Actions to the larger workflow window in sequential order
   1. Files & Folders Library : Ask for Finder Items
   2. Files & Folders Library : Label Finder Items
   3. Files & Folders Library : Get Folder Contents
   4. Files & Folders Library : Filter Finder Items
   5. Files & Folders Library : Label Finder Items
3. Apply settings as shown in this screen capture of a working application:
   

   For Label Finder Items, select in Options, Show this action when the workflow runs, so you can choose colors.

4. File menu : Save (I called mine FolderLabel) and you can put it on your Desktop, or in your /Applications folder.
   

Using list view in Finder, set the parent folder to show the sub-folders; select the ones you want to tag :

you can Command click for a specific selection, or hold the Shift key down on the parent folder, and then arrow down on your selection :

Then, using Edit Tags from the Finder toolbar :

Select the tag you want to use, or create a custom one.

Hit the Return key, and the tag will be applied to your selection :

If Edit Tags is not showing on the Finder toolbar, use Finder > View > Customize Toolbar..., and add Edit Tags.

I should have also said that you will have to expand any sub-folders to show the files, and select those as well :

An example is there how to tag files in folders or subfolders :

1. Click on go > computer > macintosh HD > library > caches

2. Now you want to tag caches folder right click on it > tags ( choose your desired colour to tag ) and in the same way caches internal files.

Finder > View > Arrange By > None