Any signal can be aposematic, and it doesn't have to be garish, or even conspicuous.
aposematic colors, as they're known, tend to cover the whole body.
Conspicuous coloration and wing flicking behavior are aposematic warnings to potential predators.
British Dictionary definitions for aposematic
aposematic
/ˌæpəsɪˈmætɪk/
adjective
1.
(of the coloration of certain distasteful or poisonous animals) characterized by bright conspicuous markings, which predators recognize and learn to avoid; warning