is it normal for someones eyes to be violet?

I don't think it's normal, but that doesn't mean people with màu tím eyes don't exist. For example, Kate Bosworth has one blue eye and one green eye; this isn't necessarily 'normal' hoặc common, but it is something that obviously exists.
'Violet' could also be interpreted in different ways. Some people read 'shocking blue eyes' and think ice-blue. Some read that same mô tả and think thêm along the lines of cerulean; some perhaps even navy.
I have never seen anyone whose eyes were violet, hoặc purple, but I'm sure that if there isn't quite a màu tím anywhere out there, there's something close.
I don't think it was something weird to be added to the book as such, I think it was thêm likely added to enhance our mental hình ảnh of Pippa's striking beauty. It was never mentioned as an everyday-beauty, like the ones bạn walk bởi on the đường phố, street on a regular basis. It seemed (at least to me) that Pippa was, if not a rarity, an intense beauty that stood out from the crowd of other visually pleasing young ladies.

I hope that made sense, and I hope it helps answer your câu hỏi :)

not necessarily violet, but some people's eyes are dark blue, and in light can seem violet. liz taylor is an example :)

Well, i'm not sure if it's normal to have màu tím eyes; however, my eyes definatly look màu tím a lot of the time. Though my eyes sometimes look blue, they are definatly màu tím at times. It usually depends on the light and what color i'm wearing. For example, if i am wearing blue, they tend to look thêm blue, but if i wear most other màu sắc they look màu tím hoặc greyish blue.

Elizabeth Taylor have màu tím eyes. Haven't bạn ever watched one of her movies?
It's not normal but some people born with this eye color.

it is not technecally normal but still apart of our reality bạn see the purpleness of eyes can be cause bởi multiple alleles for the same gene like for instance Elizabeth Taylor, who has this unique triat. So as bạn can see on a scientific level this is rare but still possable.

màu tím is part of blue eye family so few people have that color in the world. It exists.

No it is not normal. In fact a lot of eye descriptions in sách are like that. Gemma for instance. Very few people have eyes that are as green as described in the book. Most green eyes are darker and have at least a little hazel in them. But yes it is possible. And having màu tím eyes is also possible, look at Elizabeth Taylor