Make callout slightly more subtle

static/c3lingo.css

@@ -193,10 +193,10 @@ body[lang="de"] [data-lang="en"] {
   border-radius: 3px;
 }
 .callout--error {
-  background-color: rgb(148, 0, 0);
-  color: #fff;
+  background-color: #f2cdcc;
+  color: #520000;
 }
 .callout--success {
-  background-color: rgb(0, 148, 12);
-  color: #fff;
+  background-color: rgb(217, 243, 220);
+  color: rgb(1, 71, 7);
 }