Why do Kenshin's eyes change color?


When Kenshin is content and in his normal, day-to-day state, his eyes are
purple.

![Kenshin](https://i.stack.imgur.com/SDWZo.jpg)

Yet, when he is incensed or when he must resume his Hitokiri Battousai
persona, his eyes turn yellow:

![Battousai](https://i.stack.imgur.com/KqDKO.jpg)

Why do Kenshin's eyes change color?




In this [Wiki](http://kenshin.wikia.com/wiki/Himura_Kenshin), it is stated
that:

> Kenshin's eyes, too, are unusual, being a deep violet. In the anime series,
> when **Kenshin's eyes change to reflect his psychological reversion to
> Hitokiri Battōsai** , their color shifts from violet to gold.

