'Dark' in the Bible

This is the word which came to us from him and which we give to you, that God is light and in him there is nothing dark.

If we say we are joined to him, and are walking still in the dark, our words are false and our acts are untrue:

He who says that he is in the light, and has hate in his heart for his brother, is still in the dark.

But he who has hate for his brother is in the dark, walking in the dark with no knowledge of where he is going, unable to see because of the dark.