diff --git a/public/themes/bootstrap4-dark-blue/theme.css b/public/themes/bootstrap4-dark-blue/theme.css
index 2e23c74f1..6424e520f 100644
--- a/public/themes/bootstrap4-dark-blue/theme.css
+++ b/public/themes/bootstrap4-dark-blue/theme.css
@@ -5951,4 +5951,9 @@
   font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol";
 }
 
+/* Vendor extensions to the designer enhanced bootstrap compatibility */
+.fc.fc-theme-standard .fc-highlight {
+  background: #476880;
+}
+
 /* Customizations to the designer theme should be defined here */
diff --git a/public/themes/bootstrap4-dark-purple/theme.css b/public/themes/bootstrap4-dark-purple/theme.css
index 207abf3f0..968eb4e0f 100644
--- a/public/themes/bootstrap4-dark-purple/theme.css
+++ b/public/themes/bootstrap4-dark-purple/theme.css
@@ -5951,4 +5951,9 @@
   font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol";
 }
 
+/* Vendor extensions to the designer enhanced bootstrap compatibility */
+.fc.fc-theme-standard .fc-highlight {
+  background: #614c6c;
+}
+
 /* Customizations to the designer theme should be defined here */
diff --git a/public/themes/bootstrap4-light-blue/theme.css b/public/themes/bootstrap4-light-blue/theme.css
index 9260bebbf..56327c9a0 100644
--- a/public/themes/bootstrap4-light-blue/theme.css
+++ b/public/themes/bootstrap4-light-blue/theme.css
@@ -5951,4 +5951,9 @@
   font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol";
 }
 
+/* Vendor extensions to the designer enhanced bootstrap compatibility */
+.fc.fc-theme-standard .fc-highlight {
+  background: #cce5ff;
+}
+
 /* Customizations to the designer theme should be defined here */
diff --git a/public/themes/bootstrap4-light-purple/theme.css b/public/themes/bootstrap4-light-purple/theme.css
index 235b1de34..63275ccee 100644
--- a/public/themes/bootstrap4-light-purple/theme.css
+++ b/public/themes/bootstrap4-light-purple/theme.css
@@ -5951,4 +5951,9 @@
   font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol";
 }
 
+/* Vendor extensions to the designer enhanced bootstrap compatibility */
+.fc.fc-theme-standard .fc-highlight {
+  background: #e7d8ef;
+}
+
 /* Customizations to the designer theme should be defined here */