I took the original picture of this herd of sheep gathered right next to the road from the window of the car in La Manga, Spain,.
Use the Magic Wand to select the sky.
Select Inverse, and use the Lasso tool to eliminate the other sheep
You may need several tries at first. Undo if necessary.
Create a new layer and remove the background to isolate the sheep
Apply appropriate hue & saturation (colorize)
Use brush tool & paint lines swiftly (undo a gazillion times if necessary)
Apply Blend Modes such as Multiply if necessary. Reducing the opacity slightly also gives a more believable look.
Finally, paint on antennae and wings.