Final answer:
A sudden redness of the skin is called a flush, and it results from factors like emotions, medications, or temperature changes, as opposed to jaundice or cyanosis, which result from liver issues and low oxygen levels respectively.
Step-by-step explanation:
A sudden redness of the skin is known as a flush. This condition can be triggered by various factors, such as emotional states, certain medications, or rapid changes in temperature. Unlike other skin color changes, such as jaundice which is characterized by a yellow discoloration due to liver conditions, or cyanosis which refers to a blue coloration due to low oxygen levels in the blood, flushing is generally associated with increased blood flow or inflammation.