The colour "red" means love and passion. (Yellow means happiness). Also the rose (depending on what type but with this so called "the Queen Rose") means passion and love also affection and seduction.....I just had to. But thank you for a nice manga
Actually red is colour for happiness in many cultures
And red rose means love and passion but yellow rose means jealousy











http://www.mangago.zone/read-manga/boku_no_high_spec_kareshi_sama/mf/23593739800ee1184ee1ca87ab943193_chapter-3/pg-5/