Walking represents living, and usually means living according to the true things taught to us by the Lord -- to "walk in His ways." When the Lord is pictured walking, it means life itself.

4001. 'And black among the lambs' means the first state of innocence. This is clear from the meaning of 'black' as the proprium, and from the meaning of 'a lamb' as innocence, dealt with just above in 3994. The reason why 'black among the lambs' at this point means the first state of innocence is that the proprium of a person who is being regenerated rules at first, for he imagines that he does good from his proprium, and also, so that he can be granted a heavenly proprium, he must do it as if from his proprium, see 1712, 1937, 1947, 2882, 2883, 2891. This is why 'black among the lambs' here means the first state of innocence.