Translation:She has green eyes and she has blond, curly hair.
Why use uirthi at the end of the sentence instead of using aici a second time?
Wow! Thanks for the speedy answer! I just did another exercise where this occurred to me. It was in the notes at the beginning of "Characteristics." I was about to come back and correct myself, but you beat me to it.
Colours occur on a spectrum, and there aren't sharply defined boundaries between colours on the spectrum, so sometimes the names that are used for particular colours in different languages overlap, and don't line up exactly. The colour glas can also include blue-grey hues that wouldn't be described as "green" in English.
This is the entry for Glas in Dineen's 1904 dictionary:
glas, glaise, a., green, verdant (as grass); grey (as a horse or cloth); grey, bright, lustrous (of the eye); cold, inclement: lá glas, a rough, cold day; glas-aimsear, rough weather; bluish grey, as the sky; glas caorach, of natural colour, undyed (as wool).
So let me get this straight. I color is "at" someone, but hair color is "on" someone. Correct?
Note quite. External features, like hair and noses, are "on" a person, whereas they "have" eyes (tá súile ag duine).
Which earlier translation are you referring to?
In this exercise, there are two different clauses because two different prepositions are required - you use tá ... ar to say that someone "has hair" - tá gruaig fhionn uirthi, not tá gruaig fhionn aici, so the two clauses can't be combined into one in Irish. You could combine them in English, but Duolingo generally prefers that you translate the sentence as written, unless there's a compelling reason not to, and as there isn't anything particularly strange or unusual about "She has green eyes and she has blond, curly hair", that's the expected translation.
Perhaps different course creators composed these two exercises; one of them chose to repeat the subject and verb in English, and the other one didn’t. Alternatively, the same course creator composed both exercises, but did so inconsistently.