There are some older hobie hulls where deck and hull has gel coat in different colors... (Jim has one of those - yellow / red). I have never seen a Hobie with different shades of white. Hmmm, here are two theories... Your hulls might be painted while your decks might still show the original gel coat. Or, you hobie spend many years in the water, which might caused discoleration. Check here for some ideas... http://homepage.mac.com/marcusc130/Hobie/PhotoAlbum11.html