It is hard to locate a photo that shows it in color, the right year and it at the right angle. Mine is chrome, but it matches the chrome dash cover. Of course, the dash cover should be painted to match the bike. But the filler strip, I can only say...the color photos I have seen of other 'so-called correct' 1941-42 bikes, have it painted black on both a '41 and '42 model (Ref: Harley-Davidson Flatheads by Jerry Hatfield, p.79 and 80).
So, I do not recall ever seeing an answer to the question you have asked anywhere in the restoration guides. The compressed horsehair buffer underneath is mentioned in the Palmer book, just not the strip itself.
To add a little more confusion, neither have I ever found an answer to what may be your next question: "is there a trim gasket under the dash cover? (that is, one between the cover's edge and tanks.) I do not know myself. I have seen them listed for sale, and have also seen bikes both with and without. This also is not mentioned anywhere that I can find.
BTW, I do not have one.
So, maybe I have not answered your question exactly, but I ask myself this: since the tank strip is subject to potential maintenance paint damage due to the fact there is a seat 'T' grease fitting that sits in the strip's depression that has to be accessed, I believe black to be a better choice over the bike color.
I have two NOS ones right now, both black, and two different widths! I have also seen them color matched and have had painted ones in the past. I have never had an original paint '41 so cannot say from experience. In Palmer's the '39 Servi definitely has a painted one. I have lots of '41 literature and regretfully it mostly shows side views. However , look at the picture in Palmer's showing the new '41 speedo! Page 443. The bike pictured is a '41 WL and the edge of a BLACK tank filler strip is shown. Robbie
Fran-6 I have a Servi-Car prototype picture that i have tagged 41G, and it shows a black filler strip. I lifted it from an ebay auction for factory pictures a while back that i think Chris Haynes made us aware of here, but i`m not certain about my reasons for tagging it as 41G. I´ll send it over to you on e-mail as i don`t know how to post it. Please post it if you like for the others to see. Malte.