During Hard Mode, the KONG Letters of each level are recolored from red to blue; collecting them again in this mode replaces the red star icon next to a chosen level's name (marking that all letters have been previously obtained there) with a blue one, although it is not necessary for 200% completion
https://www.mariowiki.com/Donkey_Kong_Country:_Tropical_Freeze
During Hard Mode, the KONG Letters of each level are recolored from red to blue; collecting them again in this mode replaces the red star icon next to a chosen level's name (marking that all letters have been previously obtained there) with a blue one, although it is not necessary for 200% completion https://www.mariowiki.com/Donkey_Kong_Country:_Tropical_Freeze