Examples - Adjust Colors to match Blog theme

Should probably be done automatically later, instead of manually now.

web/main.dart

@@ -64,7 +64,7 @@ void createPlaceholder(Example ex) {
   // Clear Canvas
   CanvasRenderingContext2D ctx = ex.canvas.context2D;
   Point c = Point(ex.canvas.width / 2, ex.canvas.height / 2);
-  ctx.setFillColorRgb(255, 150, 10);
+  ctx.setFillColorRgb(183, 20, 39);
   ctx.fillRect(0, 0, ex.canvas.width, ex.canvas.height);
 
   // Draw Play Button