Make CSingNotes also implement Draw()

Also a bit refactoring

VocaluxeLib/Structs.cs

@@ -91,6 +91,17 @@ namespace VocaluxeLib
             A = a;
         }
 
+        public SColorF(SColorF color, float a) : this(color.R, color.G, color.B, a) {}
+        public SColorF(Color color, float a) : this(color.R / 255f, color.G / 255f, color.B / 255f, a) {}
+
+        public SColorF(Color color)
+        {
+            R = color.R / 255f;
+            G = color.G / 255f;
+            B = color.B / 255f;
+            A = color.A / 255f;
+        }
+
         [Pure]
         public Color AsColor()
         {