"As with all other Nodes in the scenegraph, Controls can be styled by using an external stylesheet, or by specifying the style directly on the Control. Although for examples it is easier to express and understand by specifying the style directly on the Node, it is recommended to use an external stylesheet and use either the styleClass or id of the Control, just as you would use the "class" or id of an HTML element with HTML CSS.
Each UI Control specifies a styleClass which may be used to style controls from an external stylesheet. For example, the Button control is given the "button" CSS style class. The CSS style class names are hyphen-separated lower case as opposed to camel case, otherwise, they are exactly the same. For example, Button is "button", RadioButton is "radio-button", Tooltip is "tooltip" and so on."
Usefult information from https://openjfx.io/javadoc/17/javafx.controls/javafx/scene/control/package-summary.html:
"As with all other Nodes in the scenegraph, Controls can be styled by using an external stylesheet, or by specifying the style directly on the Control. Although for examples it is easier to express and understand by specifying the style directly on the Node, it is recommended to use an external stylesheet and use either the styleClass or id of the Control, just as you would use the "class" or id of an HTML element with HTML CSS. Each UI Control specifies a styleClass which may be used to style controls from an external stylesheet. For example, the Button control is given the "button" CSS style class. The CSS style class names are hyphen-separated lower case as opposed to camel case, otherwise, they are exactly the same. For example, Button is "button", RadioButton is "radio-button", Tooltip is "tooltip" and so on."
Also https://openjfx.io/javadoc/17/javafx.graphics/javafx/scene/doc-files/cssref.html