I've got a 1998 770 which I've had for several years and run only off road dyed diesel fuel because of the cost difference. The percentage of dye is so little it has no effect on the engine, except for the cost savings.
A great compact utility tractor by the way. Mine has been absolutely trouble free. I've done all the servising mysefl; oil, filter, air filter, gas filter changes, adjusted the clutch, and changed the hydraulic fluid and periodic greasing. Everything is right at hand and straight forward. It starts on the first crank and works hard on a little over a half gallon - three quarters of a gallon of fuel per hour at rated engine speed. You should really enjoy this tractor.
Good luck with your 770.