Post a series that you find has no black and white areas but has gray areas instead, is shown through shades of gray

If you mean morals wise, I've always thought Black Butler was a series that pulled this off well. Everyone is extremely flawed with their own motives, there's no "bad guys" vs "good guys" since everyone is horrible or flawed in a sense.
Like the reapers are only hunting down Sebastian because they're doing their job, Sebastian is a loyal butler and helps Ciel with his goal but is only in it for his soul, Ciel is a wretched child but is a victim who went through many traumatic experiences, etcetera, etcetera...
There are very little characters who are evil just to be evil.