How can I change the icon of Recent Folder that I drag to dock on Mac 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?
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.