The person is blind. He can't pictures colors. Blind people can think in sounds and taste and smels.
Try to remember the soft skin of a baby. That's how a spring day looks like.
A forest is a place composed by sounds. There are good sounds and bad sounds. The good sounds are like velvet wispers from the lives, birds songs, the wind runing. The wind can't be seen. You can feel his carres on your face.
Try to feel some cotton. This is how clouds are looking. Neverending winds are moving them all over.