Conure color change
I have a green cheek conure, roughly 13 years old, and I have had him for about 10 years now. Everything is normal, except that recently some of his feathers have been gradually changing colors with each molt. Mostly the back of his neck (used to be blackish on head, transitioning into green back; now there is a bluish color between the head and back) and his chest/neck area (used to be grey with darker stripes; now with a hint of red on tips of chest feathers).
Other than the color changes, nothing is out of the ordinary, however I did switch him from a seed diet to a pellet diet in the last 12 months (full conversion to pellets occurred roughly 6 months ago). Is this normal for colors to change slightly as a bird ages? I'm not sure if this is a result of improved diet or simply aging.