It seems to me that "redden" and "turn red" are synonyms, and so this question should accept "Green tomatoes redden" as an answer.
Most tomatoes turn red, but not all.
I've seen both yellow and orange tomatoes in the supermarket, and I've heard off purple and green tomatoes in the wild.
I kid you not.
Yeah, there is actually a ton of varieties of tomatoes. Lemon tomatoes, zebra tomatoes, etc. It's also not that uncommon, you can pick up seeds for them in most nurseries and such.
Why does it sound like he's saying " tomatoj jur ruĝiĝas" is it just me?