Face-part tags set individual features: eye color and shape, how open the mouth is, visible teeth or tongue. Expression tags set the emotion; these set the parts. 76 tags are listed for V4.5.
Place them next to expression tags: "1girl, solo, smile, red eyes, open mouth, teeth". Eye-color tags can override the character's own color.
Top-scoring face-part tags.
V5 draws eye highlights and teeth sharply, so these tags show clearly; on V4.5 the artist style sometimes wins over part tags.
Changing the eye color changes the character.
The color tag is fighting the character tag. Lower or remove it.