XML : Auto save configuration setting into XML file and then load it using button

I'm creating a system interface and there is a setting and configuration button on it. if the button clicked it will display a panel that allow user to change the size and color of font, also could change the color of container.

what i want to do is when a user change the color of the container or font, the value of the color value will be stored automatically into XML file and because of if the user refresh the page all changes will be back to default setting, so i want to create a button that could load again all user setting that has been saved to XML file.

or if someone has other solution than using XML file, please share it with me. any links to example of fiddle or any tutorial is appreciated, i need tutorial because i'm a slow learner. help me , thank you :)