I want to move the folder recent item to dock because it helps me a lot. But this is not the only one folder i use in dock, there is another one such as download folder. Because of the icon shown on these folders based on the first item in each folder, sometime it confuses me.
The question is, can I change the icon of those folders in dock so that I can differentiate them easily?
You can easily change any icon folder from any picture you want (copy the picture you want -> get info of the folder -> click the actual picture folder -> paste the new picture).
You will also need to set your dock folders appear as a folder and not as a Stack : right click on the folder in the dock to pop up a list and choose make it appear as a folder and not as a stack (showing the last item you put in it).
To do so :
From Apple support to change picture of folder :
Create custom icons for files or folders on Mac
You can create a custom icon for any file or folder using your own pictures, icons downloaded from the web, or the icon from another file or folder.
Use your own picture or a picture from the web
On your Mac, copy the picture you want to use to the Clipboard.
One way to do this is to open the picture in the Preview app , choose Edit > Select All, then choose Edit > Copy.
Select the file or folder whose icon you want to replace, then choose File > Get Info.
At the top of the Info window, click the picture of the icon, then choose Edit > Paste.
I assume you mean the recents view from the side-bar: once you have this in the dock, then if you right click on the Recents "folder" in the dock and select the View as Folder option the Recents item will get an icon that looks like a file drawer rather than the standard folder icon–as per image below.
