Index: Core/Components/src/Core.Components.Gis/Theme/CategoryTheme.cs
===================================================================
diff -u -r2a81f01756e227d5ce93717b21b87e8a5cd5fcbb -r2534fcf82c58e32cd33a14a9d60fba9d13cf87ac
--- Core/Components/src/Core.Components.Gis/Theme/CategoryTheme.cs	(.../CategoryTheme.cs)	(revision 2a81f01756e227d5ce93717b21b87e8a5cd5fcbb)
+++ Core/Components/src/Core.Components.Gis/Theme/CategoryTheme.cs	(.../CategoryTheme.cs)	(revision 2534fcf82c58e32cd33a14a9d60fba9d13cf87ac)
@@ -20,39 +20,31 @@
 // All rights reserved.
 
 using System;
-using System.Drawing;
 
 namespace Core.Components.Gis.Theme
 {
     /// <summary>
     /// Class to define themes for categories.
     /// </summary>
-    public class CategoryTheme
+    public abstract class CategoryTheme
     {
         /// <summary>
         /// Creates a new instance of <see cref="CategoryTheme"/>.
         /// </summary>
-        /// <param name="themeColor">The color to be applied for the theme.</param>
         /// <param name="criterion">The criterion belonging to the category.</param>
         /// <exception cref="ArgumentNullException">Thrown when <paramref name="criterion"/>
         /// is <c>null</c>.</exception>
-        public CategoryTheme(Color themeColor, ValueCriterion criterion)
+        protected CategoryTheme(ValueCriterion criterion)
         {
             if (criterion == null)
             {
                 throw new ArgumentNullException(nameof(criterion));
             }
 
-            Color = themeColor;
             Criterion = criterion;
         }
 
         /// <summary>
-        /// Gets the color of the category theme.
-        /// </summary>
-        public Color Color { get; }
-
-        /// <summary>
         /// Gets the criterion that is associated with the category theme.
         /// </summary>
         public ValueCriterion Criterion { get; }
Index: Core/Components/src/Core.Components.Gis/Theme/LineCategoryTheme.cs
===================================================================
diff -u -r0c45ab7d619015e9b177a38b37a01817dd4f2f25 -r2534fcf82c58e32cd33a14a9d60fba9d13cf87ac
--- Core/Components/src/Core.Components.Gis/Theme/LineCategoryTheme.cs	(.../LineCategoryTheme.cs)	(revision 0c45ab7d619015e9b177a38b37a01817dd4f2f25)
+++ Core/Components/src/Core.Components.Gis/Theme/LineCategoryTheme.cs	(.../LineCategoryTheme.cs)	(revision 2534fcf82c58e32cd33a14a9d60fba9d13cf87ac)
@@ -37,7 +37,7 @@
         /// <param name="criterion">The <see cref="ValueCriterion"/> belonging to the category.</param>
         /// <param name="style">The <see cref="LineStyle"/> belonging to the category.</param>
         /// <exception cref="ArgumentNullException">Thrown when any parameter is <c>null</c>.</exception>
-        public LineCategoryTheme(ValueCriterion criterion, LineStyle style) : base(Color.AliceBlue, criterion)
+        public LineCategoryTheme(ValueCriterion criterion, LineStyle style) : base(criterion)
         {
             if (style == null)
             {
Index: Core/Components/src/Core.Components.Gis/Theme/PointCategoryTheme.cs
===================================================================
diff -u -r0c45ab7d619015e9b177a38b37a01817dd4f2f25 -r2534fcf82c58e32cd33a14a9d60fba9d13cf87ac
--- Core/Components/src/Core.Components.Gis/Theme/PointCategoryTheme.cs	(.../PointCategoryTheme.cs)	(revision 0c45ab7d619015e9b177a38b37a01817dd4f2f25)
+++ Core/Components/src/Core.Components.Gis/Theme/PointCategoryTheme.cs	(.../PointCategoryTheme.cs)	(revision 2534fcf82c58e32cd33a14a9d60fba9d13cf87ac)
@@ -37,7 +37,7 @@
         /// <param name="criterion">The <see cref="ValueCriterion"/> belonging to the category.</param>
         /// <param name="style">The <see cref="PointStyle"/> belonging to the category.</param>
         /// <exception cref="ArgumentNullException">Thrown when any parameter is <c>null</c>.</exception>
-        public PointCategoryTheme(ValueCriterion criterion, PointStyle style) : base(Color.AliceBlue, criterion)
+        public PointCategoryTheme(ValueCriterion criterion, PointStyle style) : base(criterion)
         {
             if (style == null)
             {
Index: Core/Components/src/Core.Components.Gis/Theme/PolygonCategoryTheme.cs
===================================================================
diff -u -r0c45ab7d619015e9b177a38b37a01817dd4f2f25 -r2534fcf82c58e32cd33a14a9d60fba9d13cf87ac
--- Core/Components/src/Core.Components.Gis/Theme/PolygonCategoryTheme.cs	(.../PolygonCategoryTheme.cs)	(revision 0c45ab7d619015e9b177a38b37a01817dd4f2f25)
+++ Core/Components/src/Core.Components.Gis/Theme/PolygonCategoryTheme.cs	(.../PolygonCategoryTheme.cs)	(revision 2534fcf82c58e32cd33a14a9d60fba9d13cf87ac)
@@ -37,7 +37,7 @@
         /// <param name="criterion">The <see cref="ValueCriterion"/> belonging to the category.</param>
         /// <param name="style">The <see cref="PolygonStyle"/> belonging to the category.</param>
         /// <exception cref="ArgumentNullException">Thrown when any parameter is <c>null</c>.</exception>
-        public PolygonCategoryTheme(ValueCriterion criterion, PolygonStyle style) : base(Color.AliceBlue, criterion)
+        public PolygonCategoryTheme(ValueCriterion criterion, PolygonStyle style) : base(criterion)
         {
             if (style == null)
             {
Index: Core/Components/test/Core.Components.Gis.Test/Theme/CategoryThemeTest.cs
===================================================================
diff -u -r47db7558d32767bc9f3635dbd4bc4506f6670523 -r2534fcf82c58e32cd33a14a9d60fba9d13cf87ac
--- Core/Components/test/Core.Components.Gis.Test/Theme/CategoryThemeTest.cs	(.../CategoryThemeTest.cs)	(revision 47db7558d32767bc9f3635dbd4bc4506f6670523)
+++ Core/Components/test/Core.Components.Gis.Test/Theme/CategoryThemeTest.cs	(.../CategoryThemeTest.cs)	(revision 2534fcf82c58e32cd33a14a9d60fba9d13cf87ac)
@@ -20,8 +20,7 @@
 // All rights reserved.
 
 using System;
-using System.Drawing;
-using Core.Common.TestUtil;
+using Core.Components.Gis.TestUtil;
 using Core.Components.Gis.Theme;
 using NUnit.Framework;
 
@@ -33,12 +32,8 @@
         [Test]
         public void Constructor_CriterionNull_ThrowsArgumentNullException()
         {
-            // Setup
-            var random = new Random(21);
-            Color themeColor = Color.FromKnownColor(random.NextEnumValue<KnownColor>());
-
             // Call
-            TestDelegate call = () => new CategoryTheme(themeColor, null);
+            TestDelegate call = () => new TestCategoryTheme(null);
 
             // Assert
             var exception = Assert.Throws<ArgumentNullException>(call);
@@ -49,18 +44,18 @@
         public void Constructor_ValidArguments_ReturnsExpectedProperties()
         {
             // Setup
-            var random = new Random(21);
-            var criterion = new ValueCriterion(random.NextEnumValue<ValueCriterionOperator>(),
-                                               string.Empty);
+            ValueCriterion criterion = ValueCriterionTestFactory.CreateValueCriterion();
 
-            Color themeColor = Color.FromKnownColor(random.NextEnumValue<KnownColor>());
-
             // Call
-            var category = new CategoryTheme(themeColor, criterion);
+            var category = new TestCategoryTheme(criterion);
 
             // Assert
-            Assert.AreEqual(themeColor, category.Color);
             Assert.AreSame(criterion, category.Criterion);
         }
+
+        private class TestCategoryTheme : CategoryTheme
+        {
+            public TestCategoryTheme(ValueCriterion criterion) : base(criterion) {}
+        }
     }
 }
\ No newline at end of file