All these words have uses to describe the change in a person’s facial appearance when he is embarrassed or under a strain. Blush is specifically restricted to the rushing of blood into the face of someone who is shocked or embarrassed: She blushed easily at any talk of bodily functions. It is more commonly used to describe a woman; a man who blushes might be thought effeminate. Colour is a less precise, almost euphemistic synonym for blush : the girl who coloured under his glance. When applied to a man, it might suggest an attempt to avoid the effeminacy implied in blush . In any case, because colour has so many other uses and can sound confusing in this context, it might best be avoided altogether.

Flush , like colour , might be used in place of blush to avoid any note of effeminacy: his face flushing at the mere mention of her name. It is more commonly used, however, to refer to a feverish condition, either from illness, exertion or exposure: their faces flushed from hours of drill and callisthenics. Flush can also indicate emotional seizures other than embarrassment: a face flushed with anger; a crowd flushed with excitement.

Redden , like colour , can substitute for blush , but in being specific about the physical change involved, it sounds less euphemistic than colour . It also, like flush , can result from other emotional seizures: a scowl reddened by rage. Both redden and colour can, of course, describe skin changes outside the present context: a face reddened by long exposure to sun and wind; the skin slowly colouring from the sharp blow.