is it normal for someones eyes to be violet?

I don't think it's normal, but that doesn't mean people with বেগুনী eyes don't exist. For example, Kate Bosworth has one blue eye and one green eye; this isn't necessarily 'normal' অথবা 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 বিবরণ and think আরো along the lines of cerulean; some perhaps even navy.
I have never seen anyone whose eyes were violet, অথবা purple, but I'm sure that if there isn't quite a বেগুনী 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 আরো likely added to enhance our mental প্রতিমূর্তি of Pippa's striking beauty. It was never mentioned as an everyday-beauty, like the ones আপনি walk দ্বারা on the রাস্তা 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 প্রশ্ন :)

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 বেগুনী eyes; however, my eyes definatly look বেগুনী a lot of the time. Though my eyes sometimes look blue, they are definatly বেগুনী 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 আরো blue, but if i wear most other রঙ they look বেগুনী অথবা greyish blue.

Elizabeth Taylor have বেগুনী eyes. Haven't আপনি 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 আপনি see the purpleness of eyes can be cause দ্বারা multiple alleles for the same gene like for instance Elizabeth Taylor, who has this unique triat. So as আপনি can see on a scientific level this is rare but still possable.

বেগুনী 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 বই 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 বেগুনী eyes is also possible, look at Elizabeth Taylor