This is a tough one. During the Napoleonic Wars Bavaria fought for France and they had a blue and white pom-pom. After they adopted the Kokarde (white-blue-white) the plume on their Raupenhelm was changed to denote service. They used red for artillery and medical, green for Jager, white for cavalry (and infantry in some cases) and red over green for engineers, called Pontonniers. I cannot find any reference to the Bavarian's ever using yellow on a plume, or on any helmet, anywhere.
The helmet is a Model 1845/48 with a Maximillian II Wappen, and it seems proper. The front and rear visors are mounted a little higher on the shell than on mine, but that's likely just a manufacturers difference. The Kokarde should be white-blue-white, but the blue paint often wears off of these. The Kokarden were many and varied in both size and style, so I would call it good if it is stamped metal.
Sorry I can't help with the plume. Please let us know if you ever figure this out.
John :?
