diff --git a/lib/Excel/Writer/XLSX/Package/Styles.pm b/lib/Excel/Writer/XLSX/Package/Styles.pm
index ae0b3592..6b588a29 100644
--- a/lib/Excel/Writer/XLSX/Package/Styles.pm
+++ b/lib/Excel/Writer/XLSX/Package/Styles.pm
@@ -794,7 +794,7 @@ sub _write_sub_border {
 
     $self->xml_start_tag( $type, @attributes );
 
-    if ( $color && $color != 64 ) {
+    if ( $color && $color ne "64" ) {
         $color = $self->_get_palette_color( $color );
 
         $self->xml_empty_tag( 'color', 'rgb' => $color );
diff --git a/t/regression/format25.t b/t/regression/format25.t
new file mode 100644
index 00000000..2175e196
--- /dev/null
+++ b/t/regression/format25.t
@@ -0,0 +1,71 @@
+###############################################################################
+#
+# Tests the output of Excel::Writer::XLSX against Excel generated files.
+#
+# Copyright 2000-2024, John McNamara, jmcnamara@cpan.org
+#
+# SPDX-License-Identifier: Artistic-1.0-Perl OR GPL-1.0-or-later
+#
+
+use lib 't/lib';
+use TestFunctions qw(_compare_xlsx_files _is_deep_diff);
+use strict;
+use warnings;
+
+use Test::More tests => 1;
+
+###############################################################################
+#
+# Tests setup.
+#
+my $filename     = 'format25.xlsx';
+my $dir          = 't/regression/';
+my $got_filename = $dir . "ewx_$filename";
+my $exp_filename = $dir . 'xlsx_files/' . $filename;
+
+my $ignore_members  = [];
+my $ignore_elements = {};
+
+
+###############################################################################
+#
+# Test the creation of a simple Excel::Writer::XLSX file with automatic color.
+#
+use Excel::Writer::XLSX;
+
+my $workbook  = Excel::Writer::XLSX->new( $got_filename );
+my $worksheet = $workbook->add_worksheet();
+
+my $format1 = $workbook->add_format(
+    border_color => '#FF9966',
+    border       => 1,
+);
+
+$worksheet->write( 2, 2, '', $format1 );
+
+$workbook->close();
+
+
+###############################################################################
+#
+# Compare the generated and existing Excel files.
+#
+
+my ( $got, $expected, $caption ) = _compare_xlsx_files(
+
+    $got_filename,
+    $exp_filename,
+    $ignore_members,
+    $ignore_elements,
+);
+
+_is_deep_diff( $got, $expected, $caption );
+
+
+###############################################################################
+#
+# Cleanup.
+#
+unlink $got_filename;
+
+__END__
diff --git a/t/regression/xlsx_files/format25.xlsx b/t/regression/xlsx_files/format25.xlsx
new file mode 100644
index 00000000..1f1238d9
Binary files /dev/null and b/t/regression/xlsx_files/format25.xlsx differ