Mutations
known proven inheritance in Pyrrhura's:-

 CINNAMON = SEX-LINKED RECESSIVE (plum eyes)
YELLOWSIDED = SEX LINKED RECESSIVE(normal eyes)
 BLUE(pastel blue) = RECESSIVE (normal eyes)
All mutations can be combined to create new colours eventually such as Steve Garvin's birds at the The Feather Tree website with his Green cheeks, " pineapple"  are a combination of yellow sided x Cinnamons.
  (Below:  Pineapple's /Yellow  sided x cinnamons)