button.setClassName("my-button"); .my-button { background-color: blue; color: white; border: 1px solid black; } button.addThemeVariants(ButtonVariant.LUMO_PRIMARY, ButtonVariant.LUMO_SMALL); button.setIcon(VaadinIcon.PLUS); button.addThemeVariants(ButtonVariant.LUMO_ICON_ALIGN_TOP); button.addClickListener(event -> { }); button.addClassName("my-button-style"); button.removeClassName("my-button-style");