Hi Sandra
I have been using Bluecol (blue coolant/antifreeze) on my R4's since the 1980's. This would be my first choice. However, I'm finding it harder to locate Bluecol these days. Last time, I resorted to using Granville (blue) as I could not find any Bluecol at the time. It has been in the radiator for a couple of years and I have no complaints.Time for a flush and refill.
Carplan and Prestone also do a blue. I cannot vouch for them as I have not tried them myself.
