lily-livered (adj.) Look up lily-livered at Dictionary.com
"cowardly," 1605, in "Macbeth;" from lily (in its color sense of "pale, bloodless") + liver (n.1), which was a supposed seat of love and passion. A healthy liver is typically dark reddish-brown. Other similar expressions: lily-handed "having white, delicate hands," lily-faced "pale-faced; affectedly modest or sensitive."