Fix FlatColorPalette default color values

src/Avalonia.Controls.ColorPicker/ColorPalettes/FlatColorPalette.cs

@@ -266,26 +266,26 @@ namespace Avalonia.Controls
             MidnightBlue9  = 0xFF1C2833,
             MidnightBlue10 = 0xFF17202A,
 
-            Pomegranate  = Pomegranate3,
-            Alizarin     = Alizarin3,
-            Amethyst     = Amethyst3,
-            Wisteria     = Wisteria3,
-            BelizeHole   = BelizeHole3,
-            PeterRiver   = PeterRiver3,
-            Turquoise    = Turquoise3,
-            GreenSea     = GreenSea3,
-            Nephritis    = Nephritis3,
-            Emerald      = Emerald3,
-            Sunflower    = Sunflower3,
-            Orange       = Orange3,
-            Carrot       = Carrot3,
-            Pumpkin      = Pumpkin3,
-            Clouds       = Clouds3,
-            Silver       = Silver3,
-            Concrete     = Concrete3,
-            Asbestos     = Asbestos3,
-            WetAsphalt   = WetAsphalt3,
-            MidnightBlue = MidnightBlue3,
+            Pomegranate  = Pomegranate6,
+            Alizarin     = Alizarin6,
+            Amethyst     = Amethyst6,
+            Wisteria     = Wisteria6,
+            BelizeHole   = BelizeHole6,
+            PeterRiver   = PeterRiver6,
+            Turquoise    = Turquoise6,
+            GreenSea     = GreenSea6,
+            Nephritis    = Nephritis6,
+            Emerald      = Emerald6,
+            Sunflower    = Sunflower6,
+            Orange       = Orange6,
+            Carrot       = Carrot6,
+            Pumpkin      = Pumpkin6,
+            Clouds       = Clouds6,
+            Silver       = Silver6,
+            Concrete     = Concrete6,
+            Asbestos     = Asbestos6,
+            WetAsphalt   = WetAsphalt6,
+            MidnightBlue = MidnightBlue6,
         };
 
         // See: https://htmlcolorcodes.com/assets/downloads/flat-design-colors/flat-design-color-chart.png