"Blue eyeliner" refers to a colored cosmetic product, specifically a pencil or liquid, used to line or accentuate the eyes in a shade of blue. Full definition
If a fine stripe of sparkle doesn't feel like enough, trace the upper lash line with blue eyeliner first. (allure.com)
With fun trends like bright blue eyeliner or more subtle trends like blush tones, there is bound to be a fall makeup trend that you will adore. (letsgothin.com)
There is this gorgeous cobalt blue eyeliner which I am in love with these days. (notonlymakeup.net)