From Administer > Site building > Home box, click on settings link in front of one of your page. This leads you to a form where you can set various options for your page.
The first thing you can set here is the number of columns your page will handle.
Please note that if change this value, you must go to the default layout of your page to re-assign blocks. Otherwise your user will have empty columns.
The next (and only for now) settings you can set are weither or not your user will be allowed to customize their blocks colors.
To let them have the ability to do so, check the option below. So if you enable this feature, you can set up 6 differents colors.
Use the color picker (you need the Colorpicker module , otherwise, inputs will only be text inputs) to select up to 6 colors. Once your done, you can click the Save configuration button.
But please don't go we are not done yet! Go now to permissions topic.