The rules haven’t changed much! A 6.5 is a Light Brown with a Mahogany tone. It should be fine to use as most of these permant colours are formulated for White coverage. If you are not sure, look for a 6.35 which is a Light Brown Golden Mahogany.
I would also rather go for L’Oreal Excellence as more people with grey hair tend to use it. If the hair line looks to bright once the time is up, just leave it on the roots a littel longer.
MIRRORS hair lab.