[David Brown]

I checked out the JG 300 website. I found a color profile plate of Bretschneider's FW 190A-7 "Red 1", March, 1944 5./JG300. The undercowling is RLM 76.
In the autumn, 1944, Bretschneider is flying a FW190A-8 (Werke Number 682204) "Red 1" - the aircraft that is the focus of Wiggy's inquiry. I believe there are 4 b&w photos of 682204.
Three of the photos are taken from aft of the main wing - port side. The underside of the cowling cannot be seen in these the pictures.
With regard to the fourth photo, it was taken forward of the main wing - port side. The underside of the cowling is in the picture, and from a layman's point of view, it does seem to be the same color as the underside - RLM 76. However, I'm not sure if this aircraft is 682204 - the mottling pattern on the front cowling seems to be the same as the others, but I cannot make out any portion of the "Rauhbautz" inscription. Also, the propeller hub seems to differ in white/black proportion -albeit, I'm comparing a prop in motion with one that is static. Anyway, maybe it's just my poor eyesight or the quality of the photos.
At this point in time, I would still go with the experts regarding the yellow or red undercowling.....but, it does make for interesting research.