from TV? LOL
several programs of the CSI/Bones/NCIS ilk where the medical examiners examine the inside of the skull to see a discolouration and in every case the medical examiner identifies it as a sub-dural haematoma. There's a problem with this, once you get through the scalp, and remove the skull the brain is covered in a tough membrane called the dura mater. Some injuries can occur on the surface of the brain between the brain and the dura mater: that's a sub-dural haematoma. Because of the relatively impermeability of the dura mater it is much less likely to cause discolouration of the skull than an extra-dural haematoma, i.e. a bleed between the skull and the dura mater.
Now sub-dural haematomas are I guess more a part of popular culture than other head injuries or fatal problems (viz. Berry aneurysms). I'm not at all sure what the likelihood that an external injury, like a blow to the head is to cause an extra-dural vs. a sub-dural haematoma, but I am relatively sure that the discolouration on the inside of the skull is less likely after a sub-dural.