PK+QP being tanked with C-Stoff. Note the dorsal panel removed to gain access to the filler opening. Water is flowing under the Komet to neutralize spillings. The left upper wing shows some paint touch-up that partially cover the Balkenkreuz. Another paint touch-up can be seen just in front of the air scoop on the rear fuselage. Note the dark color (RLM 66 is more than likely) on the inside of the canopy frame.
Source: "Messerschmitt 163 - Un avion trop loin" by Alfred Price and Jeffrey Ethell, published in "Le Fana de l'Aviation', February 1997 issue.