diff --git a/sys/dev/syscons/scterm-teken.c b/sys/dev/syscons/scterm-teken.c
index 3c8a57a981c8..4782beb99747 100644
--- a/sys/dev/syscons/scterm-teken.c
+++ b/sys/dev/syscons/scterm-teken.c
@@ -313,11 +313,11 @@ scteken_attr(const teken_attr_t *a)
 	teken_color_t fg, bg;
 
 	if (a->ta_format & TF_REVERSE) {
-		fg = a->ta_bgcolor;
-		bg = a->ta_fgcolor;
+		fg = teken_256to8(a->ta_bgcolor);
+		bg = teken_256to8(a->ta_fgcolor);
 	} else {
-		fg = a->ta_fgcolor;
-		bg = a->ta_bgcolor;
+		fg = teken_256to8(a->ta_fgcolor);
+		bg = teken_256to8(a->ta_bgcolor);
 	}
 	if (a->ta_format & TF_BOLD)
 		attr |= fgcolors_bold[fg];
diff --git a/sys/teken/teken.c b/sys/teken/teken.c
index f44969dcbb7e..c8d6b09cc33a 100644
--- a/sys/teken/teken.c
+++ b/sys/teken/teken.c
@@ -409,4 +409,55 @@ teken_state_numbers(teken_t *t, teken_char_t c)
 	return (0);
 }
 
+teken_color_t
+teken_256to8(teken_color_t c)
+{
+	unsigned int r, g, b;
+
+	if (c < 16) {
+		/* Traditional color indices. */
+		return (c % 8);
+	} else if (c >= 244) {
+		/* Upper grayscale colors. */
+		return (TC_WHITE);
+	} else if (c >= 232) {
+		/* Lower grayscale colors. */
+		return (TC_BLACK);
+	}
+
+	/* Convert to RGB. */
+	c -= 16;
+	b = c % 6;
+	g = (c / 6) % 6;
+	r = c / 36;
+
+	if (r < g) {
+		/* Possibly green. */
+		if (g < b)
+			return (TC_BLUE);
+		else if (g > b)
+			return (TC_GREEN);
+		else
+			return (TC_CYAN);
+	} else if (r > g) {
+		/* Possibly red. */
+		if (r < b)
+			return (TC_BLUE);
+		else if (r > b)
+			return (TC_RED);
+		else
+			return (TC_MAGENTA);
+	} else {
+		/* Possibly brown. */
+		if (g < b)
+			return (TC_BLUE);
+		else if (g > b)
+			return (TC_BROWN);
+		else if (r < 3)
+			return (TC_BLACK);
+		else
+			return (TC_WHITE);
+	}
+}
+
 #include "teken_state.h"
diff --git a/sys/teken/teken.h b/sys/teken/teken.h
index 4e73f7b1c8c3..aab037f2526e 100644
--- a/sys/teken/teken.h
+++ b/sys/teken/teken.h
@@ -171,4 +171,7 @@ void	teken_set_winsize(teken_t *, const teken_pos_t *);
 void	teken_set_8bit(teken_t *);
 void	teken_set_cons25(teken_t *);
 
+/* Color conversion. */
+teken_color_t teken_256to8(teken_color_t);
+
 #endif /* !_TEKEN_H_ */
diff --git a/sys/teken/teken_demo.c b/sys/teken/teken_demo.c
index 4f8a0d5e5614..49397a6c2653 100644
--- a/sys/teken/teken_demo.c
+++ b/sys/teken/teken_demo.c
@@ -116,7 +116,8 @@ printchar(const teken_pos_t *p)
 	if (px->a.ta_format & TF_REVERSE)
 		attr |= A_REVERSE;
 
-	bkgdset(attr | COLOR_PAIR(px->a.ta_fgcolor + 8 * px->a.ta_bgcolor));
+	bkgdset(attr | COLOR_PAIR(teken_256to8(px->a.ta_fgcolor) +
+	      8 * teken_256to8(px->a.ta_bgcolor)));
 	mvaddstr(p->tp_row, p->tp_col, str);
 
 	move(y, x);
diff --git a/sys/teken/teken_subr.h b/sys/teken/teken_subr.h
index 4c3106589887..32cae4dcc49d 100644
--- a/sys/teken/teken_subr.h
+++ b/sys/teken/teken_subr.h
@@ -1150,6 +1150,12 @@ teken_subr_set_graphic_rendition(teken_t *t, unsigned int ncmds,
 		case 37: /* Set foreground color: white */
 			t->t_curattr.ta_fgcolor = n - 30;
 			break;
+		case 38: /* Set foreground color: 256 color mode */
+			if (i + 2 >= ncmds || cmds[i + 1] != 5)
+				continue;
+			t->t_curattr.ta_fgcolor = cmds[i + 2];
+			i += 2;
+			break;
 		case 39: /* Set default foreground color. */
 			t->t_curattr.ta_fgcolor = t->t_defattr.ta_fgcolor;
 			break;
@@ -1163,9 +1169,35 @@ teken_subr_set_graphic_rendition(teken_t *t, unsigned int ncmds,
 		case 47: /* Set background color: white */
 			t->t_curattr.ta_bgcolor = n - 40;
 			break;
+		case 48: /* Set background color: 256 color mode */
+			if (i + 2 >= ncmds || cmds[i + 1] != 5)
+				continue;
+			t->t_curattr.ta_bgcolor = cmds[i + 2];
+			i += 2;
+			break;
 		case 49: /* Set default background color. */
 			t->t_curattr.ta_bgcolor = t->t_defattr.ta_bgcolor;
 			break;
+		case 90: /* Set bright foreground color: black */
+		case 91: /* Set bright foreground color: red */
+		case 92: /* Set bright foreground color: green */
+		case 93: /* Set bright foreground color: brown */
+		case 94: /* Set bright foreground color: blue */
+		case 95: /* Set bright foreground color: magenta */
+		case 96: /* Set bright foreground color: cyan */
+		case 97: /* Set bright foreground color: white */
+			t->t_curattr.ta_fgcolor = n - 90 + 8;
+			break;
+		case 100: /* Set bright background color: black */
+		case 101: /* Set bright background color: red */
+		case 102: /* Set bright background color: green */
+		case 103: /* Set bright background color: brown */
+		case 104: /* Set bright background color: blue */
+		case 105: /* Set bright background color: magenta */
+		case 106: /* Set bright background color: cyan */
+		case 107: /* Set bright background color: white */
+			t->t_curattr.ta_bgcolor = n - 100 + 8;
+			break;
 		default:
 			teken_printf("unsupported attribute %u\n", n);
 		}
diff --git a/sys/teken/teken_subr_compat.h b/sys/teken/teken_subr_compat.h
index 088f378af588..e93729832869 100644
--- a/sys/teken/teken_subr_compat.h
+++ b/sys/teken/teken_subr_compat.h
@@ -65,10 +65,10 @@ void
 teken_get_defattr_cons25(teken_t *t, int *fg, int *bg)
 {
 
-	*fg = cons25_revcolors[t->t_defattr.ta_fgcolor];
+	*fg = cons25_revcolors[teken_256to8(t->t_defattr.ta_fgcolor)];
 	if (t->t_defattr.ta_format & TF_BOLD)
 		*fg += 8;
-	*bg = cons25_revcolors[t->t_defattr.ta_bgcolor];
+	*bg = cons25_revcolors[teken_256to8(t->t_defattr.ta_bgcolor)];
 }
 
 static void