About: http://webisa.webdatacommons.org/145660174

Property	Value
http://www.w3.org/1999/02/22-rdf-syntax-ns#type	http://www.w3.org/ns/prov#Entity
http://www.w3.org/ns/prov#value	I can not say if this is the actual reason it was chosen, but a reason why purple is a good choice is that, other than red, it has the lowest relative luminocity of any hue.
http://www.w3.org/ns/prov#wasQuotedFrom	stackexchange.com