Wow! These are easy to do. Try this technique with turpentine and oil paint, oil pastels, acrylic, wet on wet watercolor, or wet on dry watercolor to achieve all kinds of sky variations! For this one I used a colored paper with acrylic. You can create subtler more gradiated effects using wet on wet techniques like turpentine and diluted oil paint or watercolor on wet paper.
If you don't have colored paper, dye the whole canvas or paper first, dry and then paint on top of it. Use a wide brush and long strokes to create bands of colored sky.
STEP 1 - Choose and mix your sky colors.
STEP 2 - Apply paint in wide strokes across the canvas or page.
STEP 3 - Dry and sketch figures on top or elements of a landscape. Actually, you can sketch anything including objects like fruit or dog toys. Paint them.
Try creating skies with oil pastels and turpentine or watercolor too. Vary skies by brushing on dry or wet.