Changing the icon for expand/collapse folder in windows explorer

Hi

Is it possible to change the expand/collapse image that is used in windows explorer and regedit?
At the moment mine are triangles that, when the folder is collapsed is only an outline and points to the folder name and when the folder is open the triangle is full color and point down and to the right.
What I want to do is try and give them different colors, but I have no idea where to start looking and I read the tutorials for changing the folders and thought it would be the perfect place to ask :)

its kind of what I want, but from what I can read in that oterwise great tutorial it changes the yellow folder while what I want to change is the arrow next to it.

I know if I change my theme to 1 of the high contrast ones, the arrows are turned into + for closed folders and - for open folders.. it might be part of how the whole tree-view is rendered, but if they have the images somewhere it should be possible to manipulate them

Thanks, that was just the thing

Now I can actually see the arrows on my dark theme