Hexadecimal codes? how does that help? please explain a little more. Like furan said, Photoshop is the tool that she uses and you are talking about color codes?
Here is a link explaining png:
http://en.wikipedia.org/wiki/Portable_Network_Graphics
Here is a link explaining hexadecimal color codes:
http://en.wikipedia.org/wiki/Hexadecimal_color
Otherwise could you add some details on how this works?