Cute

Blue is best.

@Muffinshire  
@PonyPon  
One eye highlight was something the character designer probably did to make her seem less cute, seeing as how fillies get 3 highlights. Ironically I think it backfired, given it makes her eyes standout more. Also in S2 males got two highlights as well.
 
The color stripes thing is actually fairly common; Mayor Mare and Celestia didn’t have any in S1 (they did in S2) and Lightning Dust doesn’t have any, either.
 
Her eyelashes are fairly unique, shared only with Mayor Mare.
 
I was pleasantly surprised they kept those things intact for Magic Duel, given her puppet had been updated.

@PonyPon  
Perhaps. She has a noticeably larger horn than unicorn fillies too, more like unicorn stallions. I doubt there was any finished animation with her as a male character, given that the script is finished and the dialogue recorded before animation, but it’s possible it’s a remnant of the character design.

@Muffinshire  
Remnant of her original status as a stallion?

@Background Pony #8485  
Not only does she have just one eye highlight, but her iris is a straight gradient without additional colour stripes in it. Usually that’s only seen on male ponies.

Colours a little off there. Also, Trixie is always always drawn with only one little eye-glint thing. Dont know why - but she is (make her look more evil?)