The five elements: metal, wood, water, fire and earth-Autumn was "metal".
Its representative color was white.
So it called autumn's dew.

The autumn was cool and fresh.
Rosy clouds in the morning or evening and temperature difference between day and night.
Night water vapour condensed into frost in the morning.

The warm sun turned water vapour into rainbow.
A boy of "white dews"was regarded cloud as cotton material and twist dew to nourish earth.