Hi Anders,
I do not have a K6, but I do have a K4. Anyhow I had a look in the Haynes great bike series 'Honda CB750 by Mike Duckworth' from the photo of the K6 on page 73, the emblem is a yellow/orange colour almost similar to the indicators.
There is also a photo on page 55 of a K1 (1970/71) with a red emblem colour similar to the rear stop light
All other photos K2,3,4,5&6 have yellow/orange emblems
Alan