Green’s Dictionary of Slang

(US) menstruation.

1931		J.T. Farrell ‘Honey, We’ll Be Brave’ in Short Stories (1937) 118: He asked her if the ‘communists’ had come, and she blushed, telling him that that was not a nice way to talk.
1999		J. Randall ‘A Visit from Aunt Rose’ in Verbatim XXV:1 Winter 25: Other visitors might include a midnight visitor (acknowledging the surprise factor), a communist (redness), the chicks, and male visitors such as the Cardinal (redness again).