Blue-black hair first had a moment back in the early 2010s, when stars like Katy Perry and Rihanna debuted the edgy color. The playful yet timeless twist on traditional black hair is now back in a big way. Celebrities like Megan Thee Stallion and Camila Mendes have been seen with new-and-improved versions of the look, proving the hue can also work on a multitude of styles, ranging from bobs to cu…