Core: Fix alpha-transparency issue in face color override. (#23532)

* Core: Fix alpha-transparency issue in face color override.

* Fix color picker opening wrongly with alpha reversed

src/Gui/TaskElementColors.cpp

@@ -173,7 +173,7 @@ public:
             }
             auto color = v.second;
             QColor c;
-            c.setRgbF(color.r, color.g, color.b, 1.0 - color.a);
+            c.setRgbF(color.r, color.g, color.b, color.a);
             px.fill(c);
             auto item = new QListWidgetItem(
                 QIcon(px),
@@ -636,3 +636,4 @@ bool TaskElementColors::reject()
 }
 
 #include "moc_TaskElementColors.cpp"
+