Hi, about your questions,
This website can be made dynamically, this means that with a php algorithm or form a database, all the colors and all the content as on your reference website can be determined, so basically your website size will be no more than just few mega witch will include all assets such as styles, images and code.
I can make your website with jquery mobile, that will give it a responsive design and cross device (desktop/mobile/tablet) capable.
Also the sitemap can be made dynamically exactly as your content, i can limit the results, and build as as many sitemaps as you want by using some limits and offsets, this means you can have how many sitemaps you want grouped/limited by how many color pages will be. the number of the pages depends on the php algorithm that will be used to generate colors.