As a fashion editor, I’m always happy to offer style advice to anyone who asks for it. Most of the time said advice pertains to weddings—what’s acceptable to wear, what isn’t, and whether or not a light shade of blue looks too white in some lights. I understand the anxiety many guests experience when an invitation comes through the letterbox; choosing an outfit for a wedding as a guest—especially a guest who identifies as a woman—can be tricky. White is still considered to be a big no-no (unless it is clearly...