、。
Actually, when you eat beets, your urine sometimes turns slightly pink.
Literal
Actually beet [object-を] eat [when-と], urine [subject-が] faintly pink-color [object-を] do [thing-こと] [subject-が] exists-[polite-ます].
A medical trivia fact (known as 'beeturia'). うっすら is a mimetic adverb for faint, barely perceptible amounts — 'slightly, thinly, faintly.' 色をする ('to be a X color') is a set pattern for describing colors — using する rather than である. ことがある ('there are times when X, sometimes X') expresses occasional possibility. ~と is the automatic conditional.