A resident expert who has catalogued cabriolet VINs supplies hard rarity data: of 1,262 VINs, only ~14 are Ruby Red (about 1%, and a late-1995 color technically for 1996); of 878 VINs, only ~6% are any shade of blue with midnight blue at ~4%. Rare, sought-after color-and-interior combinations (blue interiors especially) materially move cabriolet prices.
Color rarity, documented from a VIN census
Mercedes-Benz W124 E-Class · market