Change folder icons in Finder sidebar

I have placed my "Documents" and "Downloads" folder on another (internal) hard drive than my boot drive. I would like to have the corresponding icons again for these in the side bar, is that possible? I know that you can change the icon in the information window for each folder, but that doesn't apply to when it's in the sidebar, plus, it's a different icon anyway.

I should mention that these aren't the original Downloads and Documents folders. Just named them like that. Maybe there's a way to move the original to another drive. Thanks.

 

Yeah I'm aware that the custom set icon will still appear. But basically, it seems like there's two icons for these default folders: the one you'll see in a finder window, desktop, etc. and the ones that appear in the sidebar. These are two different types. It would be interesting to know where these are stored or how they're set!