Then I'd run traditional green coolant. I'd buy the 50/50 pre mix, then you know it was pure water it was blended with.
The yellow "universal" "long run" or gold color would be fine to run, too.
I would not run red or orange without a drain (and maybe flush) first.
You can buy "concentrate" and blend with your own water (50/50 blend), but only if it isn't super hard water, or softened water.