diff --git a/t/t4015-diff-whitespace.sh b/t/t4015-diff-whitespace.sh
index 935d101fe8..a8736f7cbe 100755
--- a/t/t4015-diff-whitespace.sh
+++ b/t/t4015-diff-whitespace.sh
@@ -491,4 +491,41 @@ test_expect_success 'combined diff with autocrlf conversion' '
 
 '
 
+# Start testing the colored format for whitespace checks
+
+test_expect_success 'setup diff colors' '
+	git config color.diff always &&
+	git config color.diff.plain normal &&
+	git config color.diff.meta bold &&
+	git config color.diff.frag cyan &&
+	git config color.diff.func normal &&
+	git config color.diff.old red &&
+	git config color.diff.new green &&
+	git config color.diff.commit yellow &&
+	git config color.diff.whitespace "normal red" &&
+
+	git config core.autocrlf false
+'
+cat >expected <<\EOF
+<BOLD>diff --git a/x b/x<RESET>
+<BOLD>index 9daeafb..2874b91 100644<RESET>
+<BOLD>--- a/x<RESET>
+<BOLD>+++ b/x<RESET>
+<CYAN>@@ -1 +1,4 @@<RESET>
+ test<RESET>
+<GREEN>+<RESET><GREEN>{<RESET>
+<GREEN>+<RESET><BRED>	<RESET>
+<GREEN>+<RESET><GREEN>}<RESET>
+EOF
+
+test_expect_success 'diff that introduces a line with only tabs' '
+	git config core.whitespace blank-at-eol &&
+	git reset --hard &&
+	echo "test" > x &&
+	git commit -m "initial" x &&
+	echo "{NTN}" | tr "NT" "\n\t" >> x &&
+	git -c color.diff=always diff | test_decode_color >current &&
+	test_cmp expected current
+'
+
 test_done
diff --git a/t/t4034-diff-words.sh b/t/t4034-diff-words.sh
index 6f7548c3a1..3f3c7577ca 100755
--- a/t/t4034-diff-words.sh
+++ b/t/t4034-diff-words.sh
@@ -35,10 +35,10 @@ aeff = aeff * ( aaa )
 EOF
 
 cat > expect <<\EOF
-<WHITE>diff --git a/pre b/post<RESET>
-<WHITE>index 330b04f..5ed8eff 100644<RESET>
-<WHITE>--- a/pre<RESET>
-<WHITE>+++ b/post<RESET>
+<BOLD>diff --git a/pre b/post<RESET>
+<BOLD>index 330b04f..5ed8eff 100644<RESET>
+<BOLD>--- a/pre<RESET>
+<BOLD>+++ b/post<RESET>
 <CYAN>@@ -1,3 +1,7 @@<RESET>
 <RED>h(4)<RESET><GREEN>h(4),hh[44]<RESET>
 
@@ -122,10 +122,10 @@ test_expect_success '--word-diff=plain --no-color' '
 '
 
 cat > expect <<EOF
-<WHITE>diff --git a/pre b/post<RESET>
-<WHITE>index 330b04f..5ed8eff 100644<RESET>
-<WHITE>--- a/pre<RESET>
-<WHITE>+++ b/post<RESET>
+<BOLD>diff --git a/pre b/post<RESET>
+<BOLD>index 330b04f..5ed8eff 100644<RESET>
+<BOLD>--- a/pre<RESET>
+<BOLD>+++ b/post<RESET>
 <CYAN>@@ -1,3 +1,7 @@<RESET>
 <RED>[-h(4)-]<RESET><GREEN>{+h(4),hh[44]+}<RESET>
 
@@ -143,10 +143,10 @@ test_expect_success '--word-diff=plain --color' '
 '
 
 cat > expect <<\EOF
-<WHITE>diff --git a/pre b/post<RESET>
-<WHITE>index 330b04f..5ed8eff 100644<RESET>
-<WHITE>--- a/pre<RESET>
-<WHITE>+++ b/post<RESET>
+<BOLD>diff --git a/pre b/post<RESET>
+<BOLD>index 330b04f..5ed8eff 100644<RESET>
+<BOLD>--- a/pre<RESET>
+<BOLD>+++ b/post<RESET>
 <CYAN>@@ -1 +1 @@<RESET>
 <RED>h(4)<RESET><GREEN>h(4),hh[44]<RESET>
 <CYAN>@@ -3,0 +4,4 @@<RESET> <RESET><MAGENTA>a = b + c<RESET>
@@ -163,10 +163,10 @@ test_expect_success 'word diff without context' '
 '
 
 cat > expect <<\EOF
-<WHITE>diff --git a/pre b/post<RESET>
-<WHITE>index 330b04f..5ed8eff 100644<RESET>
-<WHITE>--- a/pre<RESET>
-<WHITE>+++ b/post<RESET>
+<BOLD>diff --git a/pre b/post<RESET>
+<BOLD>index 330b04f..5ed8eff 100644<RESET>
+<BOLD>--- a/pre<RESET>
+<BOLD>+++ b/post<RESET>
 <CYAN>@@ -1,3 +1,7 @@<RESET>
 h(4),<GREEN>hh<RESET>[44]
 
@@ -199,10 +199,10 @@ test_expect_success 'option overrides .gitattributes' '
 '
 
 cat > expect <<\EOF
-<WHITE>diff --git a/pre b/post<RESET>
-<WHITE>index 330b04f..5ed8eff 100644<RESET>
-<WHITE>--- a/pre<RESET>
-<WHITE>+++ b/post<RESET>
+<BOLD>diff --git a/pre b/post<RESET>
+<BOLD>index 330b04f..5ed8eff 100644<RESET>
+<BOLD>--- a/pre<RESET>
+<BOLD>+++ b/post<RESET>
 <CYAN>@@ -1,3 +1,7 @@<RESET>
 h(4)<GREEN>,hh[44]<RESET>
 
@@ -231,10 +231,10 @@ test_expect_success 'command-line overrides config' '
 '
 
 cat > expect <<\EOF
-<WHITE>diff --git a/pre b/post<RESET>
-<WHITE>index 330b04f..5ed8eff 100644<RESET>
-<WHITE>--- a/pre<RESET>
-<WHITE>+++ b/post<RESET>
+<BOLD>diff --git a/pre b/post<RESET>
+<BOLD>index 330b04f..5ed8eff 100644<RESET>
+<BOLD>--- a/pre<RESET>
+<BOLD>+++ b/post<RESET>
 <CYAN>@@ -1,3 +1,7 @@<RESET>
 h(4),<GREEN>{+hh+}<RESET>[44]
 
@@ -260,10 +260,10 @@ test_expect_success 'remove diff driver regex' '
 '
 
 cat > expect <<\EOF
-<WHITE>diff --git a/pre b/post<RESET>
-<WHITE>index 330b04f..5ed8eff 100644<RESET>
-<WHITE>--- a/pre<RESET>
-<WHITE>+++ b/post<RESET>
+<BOLD>diff --git a/pre b/post<RESET>
+<BOLD>index 330b04f..5ed8eff 100644<RESET>
+<BOLD>--- a/pre<RESET>
+<BOLD>+++ b/post<RESET>
 <CYAN>@@ -1,3 +1,7 @@<RESET>
 h(4),<GREEN>hh[44<RESET>]
 
@@ -282,10 +282,10 @@ echo 'aaa (aaa)' > pre
 echo 'aaa (aaa) aaa' > post
 
 cat > expect <<\EOF
-<WHITE>diff --git a/pre b/post<RESET>
-<WHITE>index c29453b..be22f37 100644<RESET>
-<WHITE>--- a/pre<RESET>
-<WHITE>+++ b/post<RESET>
+<BOLD>diff --git a/pre b/post<RESET>
+<BOLD>index c29453b..be22f37 100644<RESET>
+<BOLD>--- a/pre<RESET>
+<BOLD>+++ b/post<RESET>
 <CYAN>@@ -1 +1 @@<RESET>
 aaa (aaa) <GREEN>aaa<RESET>
 EOF
@@ -301,10 +301,10 @@ echo '(:' > pre
 echo '(' > post
 
 cat > expect <<\EOF
-<WHITE>diff --git a/pre b/post<RESET>
-<WHITE>index 289cb9d..2d06f37 100644<RESET>
-<WHITE>--- a/pre<RESET>
-<WHITE>+++ b/post<RESET>
+<BOLD>diff --git a/pre b/post<RESET>
+<BOLD>index 289cb9d..2d06f37 100644<RESET>
+<BOLD>--- a/pre<RESET>
+<BOLD>+++ b/post<RESET>
 <CYAN>@@ -1 +1 @@<RESET>
 (<RED>:<RESET>
 EOF
diff --git a/t/test-lib.sh b/t/test-lib.sh
index 25f8bf95cd..c6afebb00d 100644
--- a/t/test-lib.sh
+++ b/t/test-lib.sh
@@ -238,14 +238,47 @@ test_set_editor () {
 }
 
 test_decode_color () {
-	sed	-e 's/.\[1m/<WHITE>/g' \
-		-e 's/.\[31m/<RED>/g' \
-		-e 's/.\[32m/<GREEN>/g' \
-		-e 's/.\[33m/<YELLOW>/g' \
-		-e 's/.\[34m/<BLUE>/g' \
-		-e 's/.\[35m/<MAGENTA>/g' \
-		-e 's/.\[36m/<CYAN>/g' \
-		-e 's/.\[m/<RESET>/g'
+	awk '
+		function name(n) {
+			if (n == 0) return "RESET";
+			if (n == 1) return "BOLD";
+			if (n == 30) return "BLACK";
+			if (n == 31) return "RED";
+			if (n == 32) return "GREEN";
+			if (n == 33) return "YELLOW";
+			if (n == 34) return "BLUE";
+			if (n == 35) return "MAGENTA";
+			if (n == 36) return "CYAN";
+			if (n == 37) return "WHITE";
+			if (n == 40) return "BLACK";
+			if (n == 41) return "BRED";
+			if (n == 42) return "BGREEN";
+			if (n == 43) return "BYELLOW";
+			if (n == 44) return "BBLUE";
+			if (n == 45) return "BMAGENTA";
+			if (n == 46) return "BCYAN";
+			if (n == 47) return "BWHITE";
+		}
+		{
+			while (match($0, /\x1b\[[0-9;]*m/) != 0) {
+				printf "%s<", substr($0, 1, RSTART-1);
+				codes = substr($0, RSTART+2, RLENGTH-3);
+				if (length(codes) == 0)
+					printf "%s", name(0)
+				else {
+					n = split(codes, ary, ";");
+					sep = "";
+					for (i = 1; i <= n; i++) {
+						printf "%s%s", sep, name(ary[i]);
+						sep = ";"
+					}
+				}
+				printf ">";
+				$0 = substr($0, RSTART + RLENGTH, length($0) - RSTART - RLENGTH + 1);
+			}
+			print
+		}
+	'
 }
 
 nul_to_q () {
diff --git a/ws.c b/ws.c
index d7b8c33f14..7302f8f5a2 100644
--- a/ws.c
+++ b/ws.c
@@ -174,8 +174,11 @@ static unsigned ws_check_emit_1(const char *line, int len, unsigned ws_rule,
 		}
 	}
 
+	if (trailing_whitespace == -1)
+		trailing_whitespace = len;
+
 	/* Check indentation */
-	for (i = 0; i < len; i++) {
+	for (i = 0; i < trailing_whitespace; i++) {
 		if (line[i] == ' ')
 			continue;
 		if (line[i] != '\t')
@@ -218,8 +221,6 @@ static unsigned ws_check_emit_1(const char *line, int len, unsigned ws_rule,
 		 * Now the rest of the line starts at "written".
 		 * The non-highlighted part ends at "trailing_whitespace".
 		 */
-		if (trailing_whitespace == -1)
-			trailing_whitespace = len;
 
 		/* Emit non-highlighted (middle) segment. */
 		if (trailing_whitespace - written > 0) {