diff --git a/sys/man/1/rio b/sys/man/1/rio
index e0b297dcb..bf225bf13 100644
--- a/sys/man/1/rio
+++ b/sys/man/1/rio
@@ -13,6 +13,9 @@ rio, label, window, wloc \- window system
 .B -s
 ]
 [
+.B -b
+]
+[
 .B -f
 .I font
 ]
@@ -92,6 +95,10 @@ The
 option initializes windows so that text scrolls;
 the default is not to scroll.
 The
+.B -b
+option reverses the normal color sheme for windows, painting white
+text on a black background.
+The
 .I font
 argument names a font used to display text, both in
 .IR rio 's
diff --git a/sys/man/4/rio b/sys/man/4/rio
index a4e680757..efab905f9 100644
--- a/sys/man/4/rio
+++ b/sys/man/4/rio
@@ -8,9 +8,16 @@ rio \- window system files
 .BI ' cmd '
 ]
 [
+.B -k
+.BI ' kbdcmd '
+]
+[
 .B -s
 ]
 [
+.B -b
+]
+[
 .B -f
 .I font
 ]
diff --git a/sys/src/cmd/rio/rio.c b/sys/src/cmd/rio/rio.c
index 605fb409b..1051a1d2d 100644
--- a/sys/src/cmd/rio/rio.c
+++ b/sys/src/cmd/rio/rio.c
@@ -46,6 +46,7 @@ Channel* initkbd(void);
 
 char		*fontname;
 int		mainpid;
+int		reverse;
 
 enum
 {
@@ -134,6 +135,9 @@ threadmain(int argc, char *argv[])
 	kbdin = nil;
 	maxtab = 0;
 	ARGBEGIN{
+	case 'b':
+		reverse = ~0xFF;
+		break;
 	case 'f':
 		fontname = ARGF();
 		if(fontname == nil)
diff --git a/sys/src/cmd/rio/wind.c b/sys/src/cmd/rio/wind.c
index 92b63c177..527c23de6 100644
--- a/sys/src/cmd/rio/wind.c
+++ b/sys/src/cmd/rio/wind.c
@@ -21,9 +21,10 @@ enum
 	MinWater	= 20000,	/* room to leave available when reallocating */
 };
 
+extern	int		reverse;	/* there are no pastel paints in the dungeons and dragons world -- rob pike */
+
 static	int		topped;
 static	int		id;
-static	int		reverse;
 
 static	Image	*cols[NCOL];
 static	Image	*grey;
@@ -43,13 +44,6 @@ wmk(Image *i, Mousectl *mc, Channel *ck, Channel *cctl, int scrolling)
 	Rectangle r;
 
 	if(cols[0] == nil){
-		/* there are no pastel paints in the dungeons and dragons world
-		 * - rob pike
-		 */
-		reverse = 0;
-		if(getenv("reverse") != nil)
-			reverse = ~0xFF;
-
 		/* greys are multiples of 0x11111100+0xFF, 14* being palest */
 		grey = allocimage(display, Rect(0,0,1,1), CMAP8, 1, 0xEEEEEEFF^reverse);
 		darkgrey = allocimage(display, Rect(0,0,1,1), CMAP8, 1, 0x666666FF^reverse);