It is when we see that internal surfaces of a body are more pink than usual, a flashy pink or too bright pink. If it is a too natural color, use red_insides instead.
It can include seeing this unusual pink on : interior of mouth, internal organs, pussy, anus, inside of nose, and other inside surfaces of body.
No requirement for internal view.

Related tags

pink_mouth, pink_pussy, pink_anus, pink_internal.
Some tags are more permissive with "pink" than pink_insides.

Inside surfaces colors

• black_insides
• purple_insides
• blue_insides
• green_insides
• yellow_insides
• orange_insides
• red_insides
• pink_insides
• white_insides

Potential conflict

When the transition between outside and inside is not the same color than the inside color, the <color>_insides tag should be from the color of inside and not from the transition.