Daphne and Susan were not supposed to be together. They especially were not supposed to be kissing in an abandoned broom closet. But here they were. Academic rivals, although not as serious about it as Granger, they had let school room tension boil over into attraction as it happens sometimes.
Susan was contemplating unbuttoning Daphne's blouse more when the bell for class change rang out.
"Shoot." they said in unison, scrabbling for their ties and cloaks.
Things collected, they gave each other a last kiss, smoothed their hair respectively and went their separate ways.
Susan didn't realize anything was wrong until she got to Charms and Hannah gave her an odd look. The other girl kept quiet though, so she returned her attention to the professor.
She kept getting glances from the other Hufflepuffs and didn't understand why. Finally during the way down to dinner, she turned and demanded to know what was so funny.
Hannah gently touched her arm, "It's your tie Sue."
"What about my tie? Isn't it the same one I wear every day?"
Justin giggled. "Only if you've moved to the dungeons."
She blinked. What was that supposed to mean?
Then she realized. Susan was colorblind. She and Daphne must have switched ties in the dark of the broom closet. Daphne must be so embarrassed. Like Susan was now. She blushed deeply as the teasing began. She bowed her head and accepted the light hearted joking from her friends, knowing they didn't care if she dated a Slytherin and wouldn't ask her to share more than she was ready for.