diff --git a/flatlaf-core/src/main/java/com/formdev/flatlaf/FlatLaf.java b/flatlaf-core/src/main/java/com/formdev/flatlaf/FlatLaf.java
index 9ff1ff0a..0b29bcdb 100644
--- a/flatlaf-core/src/main/java/com/formdev/flatlaf/FlatLaf.java
+++ b/flatlaf-core/src/main/java/com/formdev/flatlaf/FlatLaf.java
@@ -86,6 +86,7 @@ public abstract class FlatLaf
 	private static final String DESKTOPFONTHINTS = "awt.font.desktophints";
 
 	private static List<Object> customDefaultsSources;
+	private Map<String, String> extraDefaults;
 
 	private String desktopPropertyName;
 	private String desktopPropertyName2;
@@ -464,7 +465,12 @@ public abstract class FlatLaf
 	}
 
 	protected Properties getAdditionalDefaults() {
-		return null;
+		if( extraDefaults == null )
+			return null;
+
+		Properties properties = new Properties();
+		properties.putAll( extraDefaults );
+		return properties;
 	}
 
 	private void initResourceBundle( UIDefaults defaults, String bundleName ) {
@@ -779,6 +785,38 @@ public abstract class FlatLaf
 		customDefaultsSources.remove( folder );
 	}
 
+	/**
+	 * Gets extra UI defaults; or {@code null}.
+	 *
+	 * @since 1.6
+	 */
+	public Map<String, String> getExtraDefaults() {
+		return extraDefaults;
+	}
+
+	/**
+	 * Sets extra UI defaults, which are only used when setting up the application look and feel.
+	 * E.g. using {@link UIManager#setLookAndFeel(LookAndFeel)} or {@link #setup(LookAndFeel)}.
+	 * <p>
+	 * The extra defaults are useful for smaller additional defaults that may change.
+	 * E.g. accent color. Otherwise FlatLaf properties files should be used.
+	 * See {@link #registerCustomDefaultsSource(String)}.
+	 * <p>
+	 * The keys and values are strings in same format as in FlatLaf properties files.
+	 * <p>
+	 * Sample that setups "FlatLaf Light" theme with red accent color:
+	 * <pre>{@code
+	 * FlatLaf laf = new FlatLightLaf();
+	 * laf.setExtraDefaults( Collections.singletonMap( "@accentColor", "#f00" ) );
+	 * FlatLaf.setup( laf );
+	 * }</pre>
+	 *
+	 * @since 1.6
+	 */
+	public void setExtraDefaults( Map<String, String> extraDefaults ) {
+		this.extraDefaults = extraDefaults;
+	}
+
 	private static void reSetLookAndFeel() {
 		EventQueue.invokeLater( () -> {
 			LookAndFeel lookAndFeel = UIManager.getLookAndFeel();