You can apply style to the selected text inside the editor by selecting a style from the Style dropdown.

You can customize the style values in the Style dropdown in <ToolbarItem ID="Style"> section
in your language XML file under UltimateEditorInclude/Languages.

You can define a style dropdown value as follows:

<ToolbarItem ItemText="Bold Red" ItemValue="FONT-WEIGHT: bold;
COLOR: #FF0000" />

ItemText property represents the name of the style to be displayed in the Style dropdown, and
ItemValue property represents the style value to be applied to the selected text.