Water (as in: ocean) and air (sky) are both givers of life. Visible sky is water in a different form, as in mist, damp, rain or snow. All these forms are more or less transparent and hard to fetch, grab unless with a container. They share their colour palette but, depending on light and atmospheric circumstances, can take any colour or hue really.
This should be interesting enough for an art project, don’t you agree?