Deep subcutaneous injury can prolong healing time. A bruise may occur instantaneously or take 24-48 hours to rise to the skin surface. The mark may show only after a postmortem period elapses. Bruising may not occur at the same location as the site of impact because of movement of the extravasated blood through tissue layers. Bruises appearing as ante-mortem can be created during autopsy dissection or by force delivered after death.
Refrigeration can cause discoloration.
The observer may be color blind. Colors that occur early are red, blue and purple. Greens appear after 4-7 days, and yellow arrives at the seventh day. Differences which occur with injuries of varying depth are interesting. Deeper ones may take 12-24 hours before appearing.