Amazing that you've only ever driven your car a couple of times in wet, or icy weather. I would never get out of the house eight months of the year, if that was the case with my daily driver! Garages constructed of masonry can allow dampness and condensation to form on, and subsequently harm, metal surfaces, even plated finishes. I keep my car in a "Carcoon" air chamber literally all the time (as it's not been on the road since 2002), which protects from condensation, moisture and sudden temperature changes.
As to the color specifications, there are a couple of ways I would go about ensuring the finish on the brake and fuel lines is replicated. The first way would be to take a brake line off your car and get it color-matched, by making up an aerosol spray at a local auto shop, or DIY store. The second way would be to get a hard brake line part number from the L-Drive parts fiche, see if the item is still available, new, then use that as a basis to obtain the exact color-match.
I do have a couple of NOS horns that have the olive green finish applied to them, but the photograph (attached) may not be entirely representative of the true color, unfortunately, as it was taken under a fluorescent light. I have taken a picture of the olive green-finished horn next to a NOS brake line, as a comparison. There does appear to be a little color variance but, as I mentioned in my post above, that is to be expected.