at the same time, rich patrons like cosimo de medici liked to show off their wealth. they often did this by ordering paintings that had lots of bright colour and real gold backgrounds. the red colour called "vermilion" was one of the most expensive. but the most expensive colour was a beautiful blue made by grinding up a semi-precious stone called lapis lazuli. this type of painting is called "international gothic". some artists of fra angelico's day were expert at doing paintings that would make very rich people happy. but other painters, like masaccio were followers of giotto and painted in a very plain way.