Index: llvm/include/llvm/Support/WithColor.h
===================================================================
--- llvm/include/llvm/Support/WithColor.h
+++ llvm/include/llvm/Support/WithColor.h
@@ -33,11 +33,17 @@
   Remark
 };
 
+enum class ColorMode {
+  Auto,
+  Enable,
+  Disable,
+};
+
 /// An RAII object that temporarily switches an output stream to a specific
 /// color.
 class WithColor {
   raw_ostream &OS;
-  bool DisableColors;
+  ColorMode Mode;
 
 public:
   /// To be used like this: WithColor(OS, HighlightColor::String) << "text";
@@ -45,7 +51,8 @@
   /// @param S Symbolic name for syntax element to color
   /// @param DisableColors Whether to ignore color changes regardless of -color
   /// and support in OS
-  WithColor(raw_ostream &OS, HighlightColor S, bool DisableColors = false);
+  WithColor(raw_ostream &OS, HighlightColor S,
+            ColorMode Mode = ColorMode::Auto);
   /// To be used like this: WithColor(OS, raw_ostream::Black) << "text";
   /// @param OS The output stream
   /// @param Color ANSI color to use, the special SAVEDCOLOR can be used to
@@ -56,8 +63,9 @@
   /// and support in OS
   WithColor(raw_ostream &OS,
             raw_ostream::Colors Color = raw_ostream::SAVEDCOLOR,
-            bool Bold = false, bool BG = false, bool DisableColors = false)
-      : OS(OS), DisableColors(DisableColors) {
+            bool Bold = false, bool BG = false,
+            ColorMode Mode = ColorMode::Auto)
+      : OS(OS), Mode(Mode) {
     changeColor(Color, Bold, BG);
   }
   ~WithColor();
Index: llvm/lib/Support/SourceMgr.cpp
===================================================================
--- llvm/lib/Support/SourceMgr.cpp
+++ llvm/lib/Support/SourceMgr.cpp
@@ -450,8 +450,10 @@
 
 void SMDiagnostic::print(const char *ProgName, raw_ostream &OS, bool ShowColors,
                          bool ShowKindLabel) const {
+  ColorMode Mode = ShowColors ? ColorMode::Auto : ColorMode::Disable;
+
   {
-    WithColor S(OS, raw_ostream::SAVEDCOLOR, true, false, !ShowColors);
+    WithColor S(OS, raw_ostream::SAVEDCOLOR, true, false, Mode);
 
     if (ProgName && ProgName[0])
       S << ProgName << ": ";
@@ -488,8 +490,7 @@
     }
   }
 
-  WithColor(OS, raw_ostream::SAVEDCOLOR, true, false, !ShowColors)
-      << Message << '\n';
+  WithColor(OS, raw_ostream::SAVEDCOLOR, true, false, Mode) << Message << '\n';
 
   if (LineNo == -1 || ColumnNo == -1)
     return;
@@ -536,7 +537,8 @@
   printSourceLine(OS, LineContents);
 
   {
-    WithColor S(OS, raw_ostream::GREEN, true, false, !ShowColors);
+    ColorMode Mode = ShowColors ? ColorMode::Auto : ColorMode::Disable;
+    WithColor S(OS, raw_ostream::GREEN, true, false, Mode);
 
     // Print out the caret line, matching tabs in the source line.
     for (unsigned i = 0, e = CaretLine.size(), OutCol = 0; i != e; ++i) {
Index: llvm/lib/Support/WithColor.cpp
===================================================================
--- llvm/lib/Support/WithColor.cpp
+++ llvm/lib/Support/WithColor.cpp
@@ -18,8 +18,8 @@
              cl::desc("Use colors in output (default=autodetect)"),
              cl::init(cl::BOU_UNSET));
 
-WithColor::WithColor(raw_ostream &OS, HighlightColor Color, bool DisableColors)
-    : OS(OS), DisableColors(DisableColors) {
+WithColor::WithColor(raw_ostream &OS, HighlightColor Color, ColorMode Mode)
+    : OS(OS), Mode(Mode) {
   // Detect color from terminal type unless the user passed the --color option.
   if (colorsEnabled()) {
     switch (Color) {
@@ -69,7 +69,9 @@
                               bool DisableColors) {
   if (!Prefix.empty())
     OS << Prefix << ": ";
-  return WithColor(OS, HighlightColor::Error, DisableColors).get()
+  return WithColor(OS, HighlightColor::Error,
+                   DisableColors ? ColorMode::Disable : ColorMode::Auto)
+             .get()
          << "error: ";
 }
 
@@ -77,7 +79,9 @@
                                 bool DisableColors) {
   if (!Prefix.empty())
     OS << Prefix << ": ";
-  return WithColor(OS, HighlightColor::Warning, DisableColors).get()
+  return WithColor(OS, HighlightColor::Warning,
+                   DisableColors ? ColorMode::Disable : ColorMode::Auto)
+             .get()
          << "warning: ";
 }
 
@@ -85,23 +89,33 @@
                              bool DisableColors) {
   if (!Prefix.empty())
     OS << Prefix << ": ";
-  return WithColor(OS, HighlightColor::Note, DisableColors).get() << "note: ";
+  return WithColor(OS, HighlightColor::Note,
+                   DisableColors ? ColorMode::Disable : ColorMode::Auto)
+             .get()
+         << "note: ";
 }
 
 raw_ostream &WithColor::remark(raw_ostream &OS, StringRef Prefix,
                                bool DisableColors) {
   if (!Prefix.empty())
     OS << Prefix << ": ";
-  return WithColor(OS, HighlightColor::Remark, DisableColors).get()
+  return WithColor(OS, HighlightColor::Remark,
+                   DisableColors ? ColorMode::Disable : ColorMode::Auto)
+             .get()
          << "remark: ";
 }
 
 bool WithColor::colorsEnabled() {
-  if (DisableColors)
+  switch (Mode) {
+  case ColorMode::Enable:
+    return true;
+  case ColorMode::Disable:
     return false;
-  if (UseColor == cl::BOU_UNSET)
-    return OS.has_colors();
-  return UseColor == cl::BOU_TRUE;
+  case ColorMode::Auto:
+    return UseColor == cl::BOU_UNSET ? OS.has_colors()
+                                     : UseColor == cl::BOU_TRUE;
+  }
+  llvm_unreachable("All cases handled above.");
 }
 
 WithColor &WithColor::changeColor(raw_ostream::Colors Color, bool Bold,
Index: llvm/unittests/Support/CMakeLists.txt
===================================================================
--- llvm/unittests/Support/CMakeLists.txt
+++ llvm/unittests/Support/CMakeLists.txt
@@ -82,6 +82,7 @@
   UnicodeTest.cpp
   VersionTupleTest.cpp
   VirtualFileSystemTest.cpp
+  WithColorTest.cpp
   YAMLIOTest.cpp
   YAMLParserTest.cpp
   formatted_raw_ostream_test.cpp
Index: llvm/unittests/Support/WithColorTest.cpp
===================================================================
--- /dev/null
+++ llvm/unittests/Support/WithColorTest.cpp
@@ -0,0 +1,41 @@
+//===- WithColorTest.cpp --------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Support/WithColor.h"
+#include "gtest/gtest.h"
+
+using namespace llvm;
+
+TEST(WithColorTest, ColorMode) {
+  {
+    std::string S;
+    llvm::raw_string_ostream OS(S);
+    OS.enable_colors(true);
+
+    WithColor(OS, HighlightColor::Error, ColorMode::Disable) << "test";
+    EXPECT_EQ("test", OS.str());
+  }
+
+  {
+    std::string S;
+    llvm::raw_string_ostream OS(S);
+    OS.enable_colors(true);
+
+    WithColor(OS, HighlightColor::Error, ColorMode::Auto) << "test";
+    EXPECT_EQ("test", OS.str());
+  }
+
+  {
+    std::string S;
+    llvm::raw_string_ostream OS(S);
+    OS.enable_colors(true);
+
+    WithColor(OS, HighlightColor::Error, ColorMode::Enable) << "test";
+    EXPECT_EQ("\x1B[0;1;31mtest\x1B[0m", OS.str());
+  }
+}