Different colors express different moods, for example we often associate red with anger, blue with sadness. So the color can affect the mood set for you artwork. Also, in like abstract drawings it can help you because we often associate colors with certain landscapes.
it is called a suminagashi it is Ebru art and marble art
Violet is in design since in design, most designers use the use of using their own drawing design or perspective. With the use of computer- aided technology it makes it useful for designing for animation or the use of different shapes and sizes.
Hope that answers your question!
