There is no single chart that shows all available colors in all available types of Sharpie markers. As of July 2015, fine-point and ultra fine-point markers come in 31 colors, while twin-tip markers come in 20 colors, Sharpie's FAQs states Remaining marker types come in fewer colors.
The Sharpie marker page offers links to all of its marker types (including limited editions). Click on a link to go to its page and view available colors. However, special color types are also grouped together under their own link. For example, the fine-point permanent marker page allows you view the pen and ink color by hovering the mouse over each splotch of color. There are 25 splotches on the page.
Meanwhile, back on the Sharpie marker page, there are also links to fine-point markers in metallic and neon colors.