I grew those once and wasn’t sure so left some and they can grow huge. They didn’t taste as good when I left them to grow too big but were pretty good sliced and grilled with olive oil. I didn’t find colour made massive difference as seemed to turn darker at variable sizes. I found it a bit of a crap shoot but smaller = sweeter. 

One thing I did note. On the plants where I left them to grow big (good comedy as can easily get to 20lb), they produced less fruits 

 Good info, thanks.