Translation:He has a pair of green eyes.
Also translated (more literally, and correctly) as 'He has a pair of green eyes'. My first thought was '... and his other eyes are blue.' Is it just my perverted sense of humour or is the original Chinese sentence a bit contrived? How many pairs of eyes can a person be expected to have?
Someone else mentioned it above indirectly but the translation is too literal. I think the more accurate translation, in terms of the spirit of what is being said, is "His eyes are green." The sentence "He has a pair of green eyes" gives the feeling that they're not the eyes in his own head but rather some pair of maybe surgically removed eyes that he has in his possession.
These two questions have identical English translations but different Mandarin: https://forum.duolingo.com/comment/25302677 他有一双绿眼睛。= He has green eyes.
https://forum.duolingo.com/comment/25386355 他有绿眼睛。= He has green eyes.
It's not a huge deal when translating from Mandarin to English, but when going the other way it's really annoying. It's annoying because, as of writing this, they don't accept each other's Mandarin translations. As a result, when faced with translating "He has green eyes", all I can do is roll the dice and hope that I picked the right one.
"He has green eyes" should also be used. There's no need to literally say, "...a pair of green eyes". Unless you want to be more technical, where a person actually has two separate eye colours (which is very rare by the way), automatically people will think both eyes have the same colour.
I asked my co-worker who is a native speaker. Originally she said it didn't matter whether you say 绿眼睛 or 绿色的眼睛. But later when the sentence came up 黑色的小狗 she said that you need 色的. So, it seems that when there's no other adjective, you can say it either way but if there's another adjective then you need to add 色的 in between.
A good question! 'They' in the singular, as in 'that person (of gender unknown)' has a long history of usage in English and its use far predates any rule saying that 'they' must be plural.
So how does (written) Chinese handle this? Is it 他 for unspecified gender like many Indoeuropean languages, or something more like 那个人?