I don't think OEM batteries exist in Kubota equipment. Dealer installs whatever they want. Could be good, could be cheap. When it's only got a 12 month prorated warranty, it's probably a hint
I don't know about other colors.
Ken
Well, on mine,the battery have a Kubota warning label, I really doubt that a dealer would go to the trouble to use an after-market battery and put a factory warning label on it.
My guess would be that all Kubota tractors come with a battery from the factory