Meaning: This sentence is a metaphor that means the colors in the painting are moving and changing in a graceful and elegant way.
Choice of Words: Colors are the different shades we see. Dance is when we move our bodies in a way that shows how we feel. Ballet is a kind of dance that is very graceful and elegant. Canvas is the cloth that artists paint on. When we put it all together, it means that the colors in the painting are moving and changing in a graceful and elegant way, just like dancers in a ballet.