>>58734311A step-by-step guide by Yamamoto to drawing all the dexholders' eyes. Each character has a unique eye shape. The first column starting from the left, top to bottom is the Kanto characters (Red, Green, Blue, Yellow). To the right of the first column, the second column is the Johto characters (Gold, Silver, Crystal) and so on. The last column on the far right is the two Kalos characters X and Y.
The eye shapes reflect some anime personality tropes, like the characters with sharper tsurime corners to their eyes usually having more arrogant personalities, and they often chose water-type starter Pokemon (Silver, Ruby, Platinum). Characters with small pupils tend to be "intense" people in some way (Green, Gold, Silver, Pearl, berserker Ruby). Meanwhile rounded upper eyelids usually mean the character is friendlier, most of the girls have them. Upper eyelids also sloping downwards usually represent a calm and gentle personality (Yellow, Crystal, Diamond).
This is also why Scarlet
>>58732719 stands out so much, she has intense eyes for a girl dexholder matching her severe personality.