Yeah man, if you have any moisture getting inside your trunk that mat will hold water under it and rot the floor out quick ! As far a color goes, pretty sure the original color was grey .... not sure on the jack mounting !
This doesn't answer your question directly but since there was some mention of 65 and earlier trunks and the FBBO server wouldn't load pictures yesterday, this is a photo test and some early documentation. The 65 trunk pictured is an unrestored California Belvedere convertible that still has the Goodyear Power Cushion whitewall spare, the jack packed as original, and the jacking instructions on the trunk lid. There isn't a speck of rust under the liner so it does work in some cases and the splatter paint does go under the liner not body color.