Index: lib/libc/gen/err.c
===================================================================
--- lib/libc/gen/err.c
+++ lib/libc/gen/err.c
@@ -40,12 +40,14 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <unistd.h>
 #include "un-namespace.h"
 
 #include "libc_private.h"
 
 static FILE *err_file; /* file to use for error output */
 static void (*err_exit)(int);
+static int do_color = -1;
 
 /*
  * This is declared to take a `void *' so that the caller is not required
@@ -67,6 +69,42 @@
 	err_exit = ef;
 }
 
+static void
+err_pre(void)
+{
+	if (do_color == -1) {
+		if (getenv("ERRCOLOR") != NULL && isatty(fileno(err_file)))
+			do_color = 1;
+		else
+			do_color = 0;
+	}
+
+	if (do_color == 1)
+		fprintf(err_file, "\033[;31m%s: ", _getprogname());
+	else
+		fprintf(err_file, "%s: ", _getprogname());
+}
+
+static void
+err_post(void)
+{
+
+	if (do_color == 1)
+		fprintf(err_file, "\033[m\n");
+	else
+		fprintf(err_file, "\n");
+}
+
+static void
+err_post_code(int code)
+{
+
+	if (do_color == 1)
+		fprintf(err_file, "%s\33[m\n", strerror(code));
+	else
+		fprintf(err_file, "%s\n", strerror(code));
+}
+
 __weak_reference(_err, err);
 
 void
@@ -98,12 +136,12 @@
 {
 	if (err_file == NULL)
 		err_set_file(NULL);
-	fprintf(err_file, "%s: ", _getprogname());
+	err_pre();
 	if (fmt != NULL) {
 		vfprintf(err_file, fmt, ap);
 		fprintf(err_file, ": ");
 	}
-	fprintf(err_file, "%s\n", strerror(code));
+	err_post_code(code);
 	if (err_exit)
 		err_exit(eval);
 	exit(eval);
@@ -123,10 +161,10 @@
 {
 	if (err_file == NULL)
 		err_set_file(NULL);
-	fprintf(err_file, "%s: ", _getprogname());
+	err_pre();
 	if (fmt != NULL)
 		vfprintf(err_file, fmt, ap);
-	fprintf(err_file, "\n");
+	err_post();
 	if (err_exit)
 		err_exit(eval);
 	exit(eval);
@@ -163,12 +201,12 @@
 {
 	if (err_file == NULL)
 		err_set_file(NULL);
-	fprintf(err_file, "%s: ", _getprogname());
+	err_pre();
 	if (fmt != NULL) {
 		vfprintf(err_file, fmt, ap);
 		fprintf(err_file, ": ");
 	}
-	fprintf(err_file, "%s\n", strerror(code));
+	err_post_code(code);
 }
 
 void
@@ -185,8 +223,8 @@
 {
 	if (err_file == NULL)
 		err_set_file(NULL);
-	fprintf(err_file, "%s: ", _getprogname());
+	err_pre();
 	if (fmt != NULL)
 		vfprintf(err_file, fmt, ap);
-	fprintf(err_file, "\n");
+	err_post();
 }