Index: trunk/test/data/sessions/gpx_markers.jos
===================================================================
--- trunk/test/data/sessions/gpx_markers.jos	(revision 17658)
+++ trunk/test/data/sessions/gpx_markers.jos	(revision 17659)
@@ -16,5 +16,5 @@
             <file>layers/01/data.gpx</file>
         </layer>
-        <layer index="2" name="Marker layer name" type="markers" version="0.1" visible="true">
+        <layer color="#34567812" index="2" name="Marker layer name" opacity="0.5" type="markers" version="0.1" visible="true">
             <file>layers/02/data.gpx</file>
         </layer>
Index: trunk/test/unit/org/openstreetmap/josm/io/session/SessionReaderTest.java
===================================================================
--- trunk/test/unit/org/openstreetmap/josm/io/session/SessionReaderTest.java	(revision 17658)
+++ trunk/test/unit/org/openstreetmap/josm/io/session/SessionReaderTest.java	(revision 17659)
@@ -6,4 +6,5 @@
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
+import java.awt.Color;
 import java.io.ByteArrayInputStream;
 import java.io.File;
@@ -119,4 +120,8 @@
         assertEquals(gpx.getName(), "GPX layer name");
         assertEquals(marker.getName(), "Marker layer name");
+        assertEquals(1.0, gpx.getOpacity());
+        assertEquals(0.5, marker.getOpacity());
+        assertEquals(new Color(0x204060), gpx.getColor());
+        assertEquals(new Color(0x12345678, true), marker.getColor());
     }
 
Index: trunk/test/unit/org/openstreetmap/josm/io/session/SessionWriterTest.java
===================================================================
--- trunk/test/unit/org/openstreetmap/josm/io/session/SessionWriterTest.java	(revision 17658)
+++ trunk/test/unit/org/openstreetmap/josm/io/session/SessionWriterTest.java	(revision 17659)
@@ -2,4 +2,5 @@
 package org.openstreetmap.josm.io.session;
 
+import java.awt.Color;
 import java.io.File;
 import java.io.IOException;
@@ -154,5 +155,8 @@
 
     private MarkerLayer createMarkerLayer(GpxLayer gpx) {
-        return new MarkerLayer(gpx.data, "Marker layer name", gpx.getAssociatedFile(), gpx);
+        MarkerLayer layer = new MarkerLayer(gpx.data, "Marker layer name", gpx.getAssociatedFile(), gpx);
+        layer.setOpacity(0.5);
+        layer.setColor(new Color(0x12345678, true));
+        return layer;
     }