Colour changing is an odd topic for me but it has been requested.
Before I start, I just need to mention that I have read the comments and I'm aware that some colour change is natural. Even my eyes change from blue to green to gray. And hair colour changes too in the sun or with the help of dye.
This chapter is about extreme colour changes.
So, let's start with magic. If magic is common (more than the main character has magic) and this causes colour changes such as red to purple eyes, then I can accept that. We all can.
But if your main character is the only one with magic abilities and their eyes change, maybe the colour change could be left out.
I'm my opinion, it's suitability is unique to each book. If the book is fantasy, a lot more things are possible with your character. But mainly, if more than one character is affected, then I have no issues.
I'll just repeat, a Mary-Sue or any other 'perfect' character, is going to be a large number of these chapters, not just one.
I haven't wrote a chapter for this in a while.
YOU ARE READING
Anti Mary-Sue Character Guide
Non-FictionHere is just my list of tips of how to avoid creating/writing a Mary-Sue character. Take them as you wish. Greatest Achievements: #1 in non-fiction!!!