Garnier Fuctis Blue Black 210 vs L'oreal Feria Starry Night?

Feria will make it more blue, but the problem with Feria is it is a metallic dye, which means you should only use Feria or metallic dyes to dye your hair afterwards, or you could run into problems with normal dyes like Garnier giving you bad color, dryness, weird results in general. Either one of these would work, but since the blue is going to fade fast anyway you're going to be coloring it often. I would personally go with the Garnier, it makes your hair come out less damaged imo.