Told through a single scent, this is a poem about a crush, or at least a deep attraction. The speaker compares someone's perfume to candy and to a drug, two things that are sweet, tempting, and hard to resist. The perfume is strong enough to be "overpowering," and the speaker admits it makes it "harder to focus," which suggests how much the other person occupies their mind.
The most vivid moment comes in the middle, where the speaker describes a switch being flipped. A "dull gray day" turns colorful the moment this person walks by. The speaker can tell they're near just from the air growing sweet, so the smell works almost like an announcement. The qualifier "for a time at least" adds a small ache, hinting that the brightness fades once the person has passed.
The mood is warm, dreamy, and a little giddy. The language is simple and the lines are short, which fits the speaker's plain, heartfelt admiration, ending on a quiet compliment.