try conditional css and do not accept overrides

Author: sappelhoff

src/css/watermark.css

@@ -6,7 +6,20 @@
     background-position: center;
 }
 
- /* See: https://squidfunk.github.io/mkdocs-material/setup/changing-the-colors/#custom-color-schemes */
-:root {
-    --md-primary-fg-color: #ff0000;
+@media screen and (max-width: 76.1875em) {
+    .md-nav__title[for=__drawer] {
+        background-color: #ff0000 !important;
+    }
+    }
+
+.md-header {
+    background-color: #ff0000;
+}
+
+.md-main__inner {
+    background-image: url(../images/draft_watermark.png);
+    background-repeat: no-repeat;
+    background-attachment: fixed;
+    background-size: contain, cover;
+    background-position: center;
 }