Servoy offers a layered mechanism of styling the UI of solutions. 

OS/Browser Level

Smart Client Look and Feel with optional Themes, depending on the Look and Feel

Servoy StyleSheets within the solution

Object properties

OS level >>

>> SC: LAF > CSS > Property > Scripting

>> WC: Default StyleSheet > CSS > Property > Scripting (optionally: Templating)

Supported CSS

Web Client Templating

onRender event

Admin page properties related to Styling

Java Look And Feel's (LAFS)

Default LAFS

Cross platform LAFS

3rd Party LAFS