Commonly refers to lip rouge or lipstick. The French loanword ルージュ is the standard term in Japanese for cosmetic lip color.
from French
I put on lipstick before going out.
She applied lipstick to touch up her makeup.
鏡を見ながら丁寧にルージュを引いた。
I carefully applied my lipstick while looking in the mirror.
Bold lipstick really suits her.
From French 'rouge'.