diff --git a/src/calibre/gui2/convert/regex_builder.py b/src/calibre/gui2/convert/regex_builder.py
index 79d6cd490c..50136d101f 100644
--- a/src/calibre/gui2/convert/regex_builder.py
+++ b/src/calibre/gui2/convert/regex_builder.py
@@ -66,7 +66,7 @@ class RegexBuilder(QDialog, Ui_RegexBuilder):
                 self.regex.setStyleSheet('QLineEdit { color: black; background-color: rgba(0,255,0,20%); }')
                 return True
             except:
-                self.regex.setStyleSheet('QLineEdit { color: black; background-color: rgb(255,0,0,20%); }')
+                self.regex.setStyleSheet('QLineEdit { color: black; background-color: rgba(255,0,0,20%); }')
         else:
             self.regex.setStyleSheet('QLineEdit { color: black; background-color: white; }')
             self.preview.setExtraSelections([])
diff --git a/src/calibre/gui2/dialogs/metadata_bulk.py b/src/calibre/gui2/dialogs/metadata_bulk.py
index 19cec02a4d..bd90a71d03 100644
--- a/src/calibre/gui2/dialogs/metadata_bulk.py
+++ b/src/calibre/gui2/dialogs/metadata_bulk.py
@@ -884,10 +884,10 @@ class MetadataBulkDialog(QDialog, Ui_MetadataBulkDialog):
 
     def s_r_set_colors(self):
         if self.s_r_error is not None:
-            col = 'rgb(255, 0, 0, 20%)'
+            col = 'rgba(255, 0, 0, 20%)'
             self.test_result.setText(error_message(self.s_r_error))
         else:
-            col = 'rgb(0, 255, 0, 20%)'
+            col = 'rgba(0, 255, 0, 20%)'
         self.test_result.setStyleSheet('QLineEdit { color: black; '
                                        'background-color: %s; }'%col)
         for i in range(0,self.s_r_number_of_books):
diff --git a/src/calibre/gui2/search_box.py b/src/calibre/gui2/search_box.py
index 013a45a902..1ebf89f003 100644
--- a/src/calibre/gui2/search_box.py
+++ b/src/calibre/gui2/search_box.py
@@ -108,7 +108,7 @@ class SearchBox2(QComboBox):  # {{{
 
     def __init__(self, parent=None, add_clear_action=True):
         QComboBox.__init__(self, parent)
-        self.normal_background = 'rgb(255, 255, 255, 0%)'
+        self.normal_background = 'rgba(255, 255, 255, 0%)'
         self.line_edit = SearchLineEdit(self)
         self.setLineEdit(self.line_edit)
         if add_clear_action:
@@ -190,7 +190,7 @@ class SearchBox2(QComboBox):  # {{{
             self.clear(emit_search=False)
             return
         self._in_a_search = ok
-        col = 'rgba(0,255,0,20%)' if ok else 'rgb(255,0,0,20%)'
+        col = 'rgba(0,255,0,20%)' if ok else 'rgba(255,0,0,20%)'
         if not self.colorize:
             col = self.normal_background
         self.line_edit.setStyleSheet('QLineEdit{color:black;background-color:%s;}' % col)
@@ -320,7 +320,7 @@ class SavedSearchBox(QComboBox):  # {{{
 
     def __init__(self, parent=None):
         QComboBox.__init__(self, parent)
-        self.normal_background = 'rgb(255, 255, 255, 0%)'
+        self.normal_background = 'rgba(255, 255, 255, 0%)'
 
         self.line_edit = SearchLineEdit(self)
         self.setLineEdit(self.line_edit)