Answer:
Projective test
Step-by-step explanation:
Projective test - 
It is a type of personality test , which make the person respond to any ambivalent stimuli , which can disclose any secret emotions or problems present in the person's mind , is known as projective test . 
This test is also referred to as self - report test and objective test . 
Hence, from the given scenario of the question, 
Juan randomly threw colors and just created a awesome piece , depicting it to be projective test.