Add flat color preview to color picker

PlayWall/src/main/java/de/tobias/playpad/viewcontroller/design/ModernGlobalDesignViewController.java

@@ -69,6 +69,10 @@ public class ModernGlobalDesignViewController extends NVC {
 		flatDesignCheckbox.selectedProperty().addListener((a, b, c) ->
 		{
 			design.setFlatDesign(c);
+
+			// Update button preview
+			backgroundColorButton.setStyle(getLinearGradientCss(design.getBackgroundColor()));
+			playColorButton.setStyle(getLinearGradientCss(design.getPlayColor()));
 		});
 
 		infoLabelFontSizeComboBox.getItems().addAll(9, 10, 12, 13, 14, 16, 18, 20, 24, 28);

PlayWallCore/src/main/java/de/tobias/playpad/design/modern/ModernColor.java

 package de.tobias.playpad.design.modern;
 
 import de.tobias.playpad.DisplayableColor;
+import de.tobias.playpad.profile.Profile;
 import de.tobias.playpad.util.FadeableColor;
 import javafx.scene.paint.*;
 
@@ -106,9 +107,13 @@ public enum ModernColor implements DisplayableColor {
 
 	@Override
 	public Paint getPaint() {
+		if (Profile.currentProfile().getProfileSettings().getDesign().isFlatDesign()) {
+			return Color.web(paint());
+		} else {
 			return new LinearGradient(0, 0, 0, 1, true, CycleMethod.NO_CYCLE, new Stop(0, Color.web(colorHi)),
 					new Stop(1, Color.web(colorLow)));
 		}
+	}
 
 	public String linearGradient() {
 		return "linear-gradient(" + getColorHi() + "," + getColorLow() + ")";