I was watching it before and noticed that her eyes don't seem to have the same color. Is this how she is naturally, part of the character, or were my eyes playing tricks on me?
Melissa Benoist actually has the same color in both Iris's, what you're seeing is an injury she suffered that effected her pupil sizes. It is the same thing that David Bowie has. He was punched directly in the eye, which caused one pupil to be a larger size than the other all the time. Where normally your pupil shrinks or expands in a sense, one of her eyes is not able to do so do to the injury's impact, leaving it more or less permanently enlarged.