diff --git a/variables.tf b/variables.tf
index fbc352b..7060880 100644
--- a/variables.tf
+++ b/variables.tf
@@ -69,11 +69,11 @@ variable "tags" {
       length(v) <= 256 &&
       (
         # Allow either production format or test format
-        can(regex("^[\\w\\s+=.@-]*$", k)) && can(regex("^[\\w\\s+=.@-]*$", v)) ||
+        can(regex("^[\\w\\s+=.:@-]*$", k)) && can(regex("^[\\w\\s+=.:@-]*$", v)) ||
         can(regex("^environment$", k)) && can(regex("^test$", v)) # Special case for test environment
       )
     ])
-    error_message = "Tag keys must be <= 128 chars, values <= 256 chars, and both can only contain alphanumeric characters, spaces, and '.+-=@_'. For test environment, use 'environment': 'test'."
+    error_message = "Tag keys must be <= 128 chars, values <= 256 chars, and both can only contain alphanumeric characters, spaces, and '.+-=@_:'. For test environment, use 'environment': 'test'."
   }
 }