This is the earliest known coloured image of the Dannebrog (Danish flag)
Baron Hastings (temp. Edward III, 1295 creation, also shown in the Gelre Armorial, c. 1390s) and in coats of arms derived from the Hastings one, e.g. Edmund Grey, 1st Earl of Kent (d. 1490).
Such publications, akin to Almanach de Gotha or Gelre Armorial and descended from the tradition of rolls of arms, appeared in Poland regularly from 15th century onwards.