The term 'become pale' can be expressed in two ways: BLANCH (6 letters) and turn as white as a sheet (15 letters). BLANCH is a verb that means to become pale or to whiten, usually through the use of steam, boiling water, or chemical action. The phrase 'turn as white as a sheet' is an idiom that means to become very pale, usually due to fear, shock, or surprise. Both expressions are used to describe a person's skin color becoming much paler than usual.