One of the simplest ways to achieve a scaly mermaid makeup look is by using fishnet tights or a wig cap. As mentioned on Cosmopolitan, stretching one of these over your head and across your face creates a stencil that you can fill in using makeup.

The specific products and colors you use are ultimately up to you, as you can use the fishnet hack to create completely different looks depending on what you're going for.

Kathlyn Celeste uses products like a BH Cosmetics eyeshadow palette and an Anastasia Beverly Hills highlighter set to achieve her purple and blue look (via YouTube). For a darker purple style, shivonmakeupbiz used a mixture of greens, blues, and purples from various Urban Decay palettes (via YouTube).

You can create an ombre look by flowing one color into another or fade out the scales into your skin by using leftover eyeshadow on your brush in the same color as your scales. While applying the makeup, it's recommended that you dab your applicator instead of brushing, as you don't want the scales to run together.

Once you carefully remove your makeshift stencil and reveal your beautiful scales, you can add as much glitter and jewels as you want to complete your mermaid Halloween look.