Add layer background

src/ol/color.js

@@ -213,7 +213,7 @@ export function toString(color) {
   if (b != (b | 0)) {
     b = (b + 0.5) | 0;
   }
-  const a = color[3] === undefined ? 1 : color[3];
+  const a = color[3] === undefined ? 1 : Math.round(color[3] * 100) / 100;
   return 'rgba(' + r + ',' + g + ',' + b + ',' + a + ')';
 }