Mine was based off the latest story in the comics so he doesn’t look like the traditional joker but the only thing different about the hair would be the style.
The particle settings weren’t too complicated, just had to make sure I had enough hair so I set the emission to 8000 and children to 5. I used particle edit mode to cut/style his hair so there aren’t really 8000 strands. Make sure the size of the strands are small and that the tip is thinner than the root.
I used a tutorial from blender cookie to make the shader. The musgrave texture is used to add some variation in the color of the hair. The hair info node is used to make the roots a bit darker and then I combined them and used it to control the shade of green. I then mix the diffuse node with the hair bdsf nodes which control the spec/reflection and how soft the hair looks when the rim light hits it.