@Nep The kanji in Japanese are:
「佐藤」 Satou (FMC's family name)
「砂糖」 Satou (sugar)
「武藤」 Mutou (MMC's family name)
「無糖」 Mutou (sugarless)
So they're homophones. That said, you guys could still be onto something given that they're described here as "sugary" (pink) and "bittersweet" (blue).
@greatninja3 Went and added it. Thanks.
Edit: And somebody else removed it. :/ I don't see how this isn't a romance series, so I'm adding it back again.