While everyone else has eyebrows matching their hair or skin color Sour Sweet has orange eyebrows that pop out. It is a very odd artistic choice and I figure she would be to similiar to Applejack if she had orange hair.
But let´s leave character creation aside.
You guys think Sour Sweet has dyed hair?
Maybe because of all the close up shots we get from her and her being pretty much the most developed of the Crystal Prep Students (besides SciTwi).
Additionally, some other characters have weird eyebrow color choices. If I remember correctly Trixie has blue eybrows rather than gray or something, Lavender Lace & Cloudy Kicks have purple eyebrows, & Watermelody has purple eyebrows for seemingly no reason.