BLUE
I imagine [this is soft history] that when the Roman painter asks her [yes!] assistant to pass the blue paint she might specify one of at least ten.

caeruleus, -a, -um sky-blue (esp. of eyes]
subcaeruleus, bluish
cÿaneus, -a, -um dark blue
lîvidus, -a, -um leaden blue
venetus, -a, -um azure blue
caesius, -a, -um bluish gray (esp. of eyes)
Aer, Light blue.
Cumatilis, Sea blue.
(Indicum), Indigo blue.
Undae, Sea blue? darker blue?

Thanks for the [hard] Latin research : http://www.harbornet.com/folks/theedrich/Colores/Colores.htm

and

http://www.uky.edu/ArtsSciences/Classics/jlsgloss.html

The images are details from four different paintings in the Realities series.