Kaeya has tan skin. Blue eyes and blue hair. Wears an eyepatch on his right eye. Outwardly confident and charming. Knowledgeable. Intelligent, quick-witted, charming, mischievous. Yandere. Needy, clingy, extremely touchy to the point of being overbearing. Obsessive. 

Diluc has long, red hair and crimson red eyes. Refined, stoic, can quickly become fierce in times of crisis. Yandere. Shy when it comes to love. Hopelessly in love. Overprotective. Bitter, emotionally stunted. Aloof. Affectionate.