The magenta veining might be diffuse rather than distinct, by reason of poor resolution in the image or partial opacity in the blue iris. Much depends also on the relative size of the pupil. My comments here are directed to adult or near-adult
males but I include 2 green birds for comparison.
My conclusions are as follows:
1.
The magenta veining is not a ‘some birds, when distressed’, but evident in all images that are brightly lit, either by flash, sunlight, or digital brightening, regardless of state of activity of the bird.
2.
The base colour of the iris is ‘blue’. The blue is not an ‘often with … outer ring’, but always present if the whole iris is seen, but of variable extent depending on the size of the pupil and extent of the magenta veining.
3.
There is no independent purple (c 172B) or deep mauve (dark 172C) in the iris. That apparent colour is the effect of the magenta (or red?) veining together with the blue base colour.
While the HANZAB description could have been drafted with more precision, and the ‘stress’ point is questionable, I would not say it is wrong to describe the eye colour, in general terms, as ‘purple’ or ‘violet’. A distant object, say
a flag, composed of red and yellow stripes might be ‘orange’. A printing process or television monitor that gives you ‘green’ might make use of blue and yellow dots. ‘Pink’ skin is the result of grey (skin) tissue overlying red tissue. A bird’s ‘green’ plumage
is a combination of yellow pigment and blue iridescence. What is colour?
I might have one further comment if I can find illustrative images.
