Great idea
I just found some paint in a corner, somewhere in a warehouse, and I said to try to use them for a noble purpose :)) I did not have too many color options, or any other kind of cardboard, excepting black, with a little texture on it.
I began to pour many layers of paint, then I lifted it upright the cardboard and let them flow... I loved how to combine and continued... I was amazed to see how the colors combine and flow together, in a delicate dance...