Index: src/kmessagewidget.cpp
===================================================================
--- src/kmessagewidget.cpp
+++ src/kmessagewidget.cpp
@@ -32,6 +32,115 @@
 #include <QToolButton>
 #include <QStyle>
 
+#include <QStandardPaths>
+#include <QSettings>
+#include <QDebug>
+
+//---------------------------------------------------------------------
+// KGlobalSettings
+// A basic interface to read the global KDE settings store (kdeglobals)
+//---------------------------------------------------------------------
+class KGlobalSettings
+{
+public:
+    KGlobalSettings(const QString &initialGroup = QString())
+    {
+        const QString kdeGlobals = QStandardPaths::locate(QStandardPaths::ConfigLocation, QStringLiteral("kdeglobals"));
+        if (!kdeGlobals.isEmpty()) {
+            m_settings = new QSettings(kdeGlobals, QSettings::IniFormat);
+        }
+        if (m_settings && !initialGroup.isEmpty()){
+            if (m_settings->childGroups().contains(initialGroup)) {
+                m_settings->beginGroup(initialGroup);
+            } else {
+                delete m_settings;
+                m_settings = nullptr;
+            }
+        }
+    }
+
+    virtual ~KGlobalSettings()
+    {
+        delete m_settings;
+    }
+
+    QColor readRGBRaw(const QString &key, QColor value = QColor())
+    {
+        if (m_settings && m_settings->contains(key)) {
+            QStringList rgb = m_settings->value(key).toStringList();
+            if (rgb.size() >= 3) {
+                QColor newValue(rgb.at(0).toInt(), rgb.at(1).toInt(), rgb.at(2).toInt());
+                if (newValue.isValid()) {
+                    value = newValue;
+                }
+            }
+        }
+        return value;
+    }
+
+    QColor readRGB(const QString &key, QColor value = QColor())
+    {
+        // 
+        if (qEnvironmentVariableIsSet("KMESSAGEWIDGET_BACKGROUND_BRIGHTNESS_MATCHED")) {
+            return readRGBMatched(key, value);
+        } else {
+            return readRGBRaw(key, value);
+        }
+    }
+
+    // read an RGB triplet from <key> in the currently active group, or return
+    // the default <value> if the key doesn't exist. The returned RGB value is
+    // corrected so that its brightness is as close as possible to the brightness
+    // of the default colour.
+    QColor readRGBMatched(const QString &key, QColor value = QColor())
+    {
+        qreal defaultBrightness = value.isValid() ? psychoMetricBrightness(value) : -1;
+        qWarning() << "Default intensity for key" << key << ":" << defaultBrightness;
+        if (m_settings && m_settings->contains(key)) {
+            QStringList rgb = m_settings->value(key).toStringList();
+            if (rgb.size() >= 3) {
+                QColor newValue(rgb.at(0).toInt(), rgb.at(1).toInt(), rgb.at(2).toInt());
+                if (newValue.isValid()) {
+                    qreal newBrightness = psychoMetricBrightness(newValue);
+                    if (defaultBrightness >= 0 && newBrightness > 0) {
+                        // determine the largest factor by which we can scale the RGB
+                        // triplet to approach the reference brightness as much as possible.
+                        qreal brightnessScaleFactor = defaultBrightness / newBrightness;
+                        qreal maxRGB = newValue.redF();
+                        if (newValue.greenF() > maxRGB) {
+                            maxRGB = newValue.greenF();
+                        }
+                        if (newValue.blueF() > maxRGB) {
+                            maxRGB = newValue.blueF();
+                        }
+                        if (maxRGB * brightnessScaleFactor > 1) {
+                            brightnessScaleFactor = 1 / maxRGB;
+                        }
+                        qWarning() << "brightness scaling:" << newBrightness << ":"
+                            << brightnessScaleFactor << "*" << newValue.redF() << newValue.greenF() << newValue.blueF();
+                        value.setRgbF(newValue.redF() * brightnessScaleFactor
+                            , newValue.greenF() * brightnessScaleFactor
+                            , newValue.blueF() * brightnessScaleFactor);
+                    } else {
+                        value = newValue;
+                    }
+                    qWarning() << "New intensity:" << psychoMetricBrightness(value);
+                }
+            }
+        }
+        return value;
+    }
+
+private:
+    // calculate the perceived (psycho-metric) brightness for an RGB triplet
+    qreal psychoMetricBrightness(QColor rgb)
+    {
+        return 0.299 * rgb.redF() + 0.586 * rgb.greenF() + 0.115 * rgb.blueF();
+    }
+
+    QSettings *m_settings = nullptr;
+};
+
 //---------------------------------------------------------------------
 // KMessageWidgetPrivate
 //---------------------------------------------------------------------
@@ -258,30 +367,34 @@
 {
     d->messageType = type;
     QColor bgBaseColor;
+    const QPalette palette = QGuiApplication::palette();
 
-    // We have to hardcode colors here because KWidgetsAddons is a tier 1 framework
-    // and therefore can't depend on any other KDE Frameworks
-    // The following RGB color values come from the "default" scheme in kcolorscheme.cpp
+    // We cannot use KColorScheme here because KWidgetsAddons is a tier 1 framework
+    // and therefore can't depend on any other KDE Frameworks. We thus try to get
+    // the colours that interest us directly from the global settings store using QSettings.
+    // It that fails we use hardcoded colours, or the highlight colour (for Information).
+    // The hardcoded RGB color bgBaseColors come from the "default" scheme in kcolorscheme.cpp
+    KGlobalSettings settings(QStringLiteral("Colors:Window"));
     switch (type) {
     case Positive:
-        bgBaseColor.setRgb(39, 174,  96); // Window: ForegroundPositive
+        bgBaseColor = settings.readRGB(QStringLiteral("ForegroundPositive"), QColor(39, 174, 96));
         break;
     case Information:
-        bgBaseColor.setRgb(61, 174, 233); // Window: ForegroundActive
+        bgBaseColor = settings.readRGB(QStringLiteral("ForegroundActive"), palette.highlight().color());
         break;
     case Warning:
-        bgBaseColor.setRgb(246, 116, 0); // Window: ForegroundNeutral
+        bgBaseColor = settings.readRGB(QStringLiteral("ForegroundNeutral"), QColor(246, 116, 0));
         break;
     case Error:
-        bgBaseColor.setRgb(218, 68, 83); // Window: ForegroundNegative
+        bgBaseColor = settings.readRGB(QStringLiteral("ForegroundNegative"), QColor(218, 68, 83));
         break;
     }
     const qreal bgBaseColorAlpha = 0.2;
     bgBaseColor.setAlphaF(bgBaseColorAlpha);
 
-    const QPalette palette = QGuiApplication::palette();
     const QColor windowColor = palette.window().color();
-    const QColor textColor = palette.text().color();
+    // prefer the theme's normal foreground colour for text for more reliable readability with dark themes
+    const QColor textColor = settings.readRGBRaw(QStringLiteral("ForegroundNormal"), palette.text().color());
     const QColor border = bgBaseColor;
 
     // Generate a final background color from overlaying bgBaseColor over windowColor