CanIUseCss

How to style applications by means of CSS

The most comprehensive way would be to get a theme for ExtJS. Currently Kitto uses ExtJS 3.4, but will be ported to ExtJS 5.x quite soon. Once a theme is installed in your ExtJS directory, you can have a Kitto application use it by adding

Ext:
  Theme: my-theme

to your config file

You can also customize individual CSS styles by adding code to your Home/Resources/js/application.css file (which is included in every Kitto application by default). For example, if you want to have bigger text in buttons, you would do something like this:

.x-btn button {
    font-size: 125%;
}

In order to learn the structure and naming of ExtJS styles, we suggest you to explore the generated pages with a debugger such as Firebug.

There are also ways to include additional CSS files and assign individual CSS classes to your GUI objects if you create custom controllers.