I overheard a conversation while on the elevator the other day involving one woman, who was wearing a black top with a navy sweater, telling another woman that if her daughter saw her wearing black and blue together that she would be appalled. Well no offense, but it sounds like her daughter doesn’t know what she is talking about! Rules like not mixing black and blue and or not wearing white after Labor Day are so passe.
I personally love the combination of black and blue as long as it is intentional. Go for a clearly distinct blue hue and not a navy that is so dark that it could be mistaken for black. This gives enough contrast, broadening the possibilities in your wardrobe.