Danny Boy Blue is a true colbalt blue, quite vivid similar to the original Sally Hansen Pacific Blue or Nails Inc Baker Street. No mistaking this for black or even a white, certainly a blue.
Dragons at Dusk is a beautiful duochrome polish, changing from blue to purple, there is also some teal in there too which is nice.
Which means the winner is The First Avenger which is a beautiful metallic primarily blue but a duochrome changing to purple on different angles.