Gary We did the water pump on our 8.3 Cummins at end of harvest!I had local truck fix it company apprentice come out and install a exchange water pump! we had to drain out coolant (Tec50) and reuse old green coolant, and had to top it up with new coolant! the top up was blue where as the old coolant was green! I sort of gave a bit of a gasp when topping up radiator in R62! and young guy said straight away that the new coolant is blue, where as the older heated once coolant turns to green! this is so called, to stop shops from draining out coolant and just reusing it back in engines, and making customer pay full tote odds for a coolant change! ( like anyone is going to check the coolant level before you leave the garage!) So! its quite normal for it to be blue when new and green once its been heated up to what ever temp it gets to to make it turn green! Do a test in a coffee tin over a BBQ! see what happens. Rolf