This is interesting in my case compared with Rick.
Hanna measurement is more or less same as Salifert (Hanna ; 7.3 and Salifert 7.3 -7.7- 7.3 is noted as color. Start to change and 7.7 is that the color is not further pinker. ) KHG is 6.3.
With reference to the very consistent measurement of KHG, I decide to adj. the measurement by adding 1dKH.
I really don't think there is anything wrong with this tactic. I chose not to make an adjustment, because all of the information that my corals and tank were giving me was that i was actually running 1 dKH low. Since having raised it up there has been rapid and dramatic changes, so I think my experience in reading my tank was correct. (Always trust your gut instinct).