Anish Kapoor
Anish Kapoor is also famous for a fight with other artists about black paint.  When scientists invented a material called "Vantablack", Kapoor made a deal with them: He bought exclusive rights.  This means he paid the company that owned Vantablack to let him be the only artist allowed to use Vantablack in art.  Vantablack could be used to paint something so black that a flat circle would look like a deep hole.  Other artists were angry with Kapoor because they wanted to use this paint too.  One artist, Stuart Semple, made other paints, for example "Pinkest Pink" and "Better Black", and wrote on his website that Kapoor could not have any.  Anyone buying the paint had to promise not to give any to Kapoor.  Kapoor got some Pinkest Pink anyway and put a picture of himself on Instagram.