The example site (sleepywrap.point4design) uses javascript for all its functions. You can't even see the site without js.
You can't get a text box added to a radiobutton, at least not in the stock Zen Cart setup, but you can easily rework the problem so it disappears.
Instead of having the colors be radiobuttons or checkboxes of one "Color" option name, make each color an option name, dropdown type, and give them option values of 0, 1, 2, 3, etc. When adding attributes to the product, make 0 the default, and assign the total price for that quantity. In the product editing page, make the product priced by attributes with base price of 0.
This will show each color with a quantity box where a quantity can be selected. When the product is added to cart, the total will reflect all the color selections, saying Blue 1, Red 3, etc., with the total price. It will probably also say Green 0; I haven't tested the setup to be sure.



