first try

src/main/java/ninja/javafx/smartcsv/fx/SmartCSV.java

@@ -85,6 +85,9 @@ public class SmartCSV extends Application {
     private void showUI(Stage primaryStage, String name, String version) {
         SmartCSVController smartCVSController = appContext.getBean(SmartCSVController.class);
         Scene scene = new Scene((Parent) smartCVSController.getView());
+        var darkThemeCss = scene.getRoot().getStylesheets().get(0);
+        scene.getRoot().getStylesheets().remove(darkThemeCss);
+        scene.getRoot().getStylesheets().add(darkThemeCss);
 
         primaryStage.setScene(scene);
         primaryStage.setTitle(String.format("%s %s", name, version));

src/main/resources/ninja/javafx/smartcsv/fx/dark-theme.css

@@ -0,0 +1,34 @@
+.root {
+    -fx-base: rgb(39, 40, 40);
+    -fx-accent: rgb(80, 80, 80);
+    -fx-default-button: rgb(39, 40, 40);
+    -fx-focus-color: rgb(80, 80, 80);
+    -fx-faint-focus-color: #efefef22;
+    -fx-focused-text-base-color : ladder(
+            -fx-selection-bar,
+            -fx-light-text-color 45%,
+            -fx-dark-text-color 46%,
+            -fx-dark-text-color 59%,
+            -fx-mid-text-color 60%
+    );
+    -fx-focused-mark-color : -fx-focused-text-base-color ;
+    -fx-control-inner-background: rgb(39, 40, 40);
+    -fx-control-inner-background-alt: rgb(20, 20, 20);
+}
+
+
+.table-row-cell:selected {
+    -fx-background-color: rgb(80, 80, 80);
+}
+.table-row-cell {
+    -fx-background-color: #81c483;
+}
+.text-input:focused {
+    -fx-highlight-text-fill: ladder(
+            -fx-highlight-fill,
+            -fx-light-text-color 45%,
+            -fx-dark-text-color  46%,
+            -fx-dark-text-color  59%,
+            -fx-mid-text-color   60%
+    );
+}

src/main/resources/ninja/javafx/smartcsv/fx/smartcsv.fxml

@@ -266,6 +266,7 @@
     <left>
     </left>
     <stylesheets>
+        <URL value="@/ninja/javafx/smartcsv/fx/dark-theme.css" />
         <URL value="@/ninja/javafx/smartcsv/fx/smartcsv.css" />
     </stylesheets>
     <bottom>