diff --git a/clang/tools/diagtool/TreeView.cpp b/clang/tools/diagtool/TreeView.cpp
--- a/clang/tools/diagtool/TreeView.cpp
+++ b/clang/tools/diagtool/TreeView.cpp
@@ -27,24 +27,13 @@
 }
 
 class TreePrinter {
+  using Colors = llvm::raw_ostream::Colors;
+
 public:
   llvm::raw_ostream &out;
-  const bool ShowColors;
   bool Internal;
 
-  TreePrinter(llvm::raw_ostream &out)
-      : out(out), ShowColors(hasColors(out)), Internal(false) {}
-
-  void setColor(llvm::raw_ostream::Colors Color) {
-    if (ShowColors)
-      out << llvm::sys::Process::OutputColor(static_cast<char>(Color), false,
-                                             false);
-  }
-
-  void resetColor() {
-    if (ShowColors)
-      out << llvm::sys::Process::ResetColor();
-  }
+  TreePrinter(llvm::raw_ostream &out) : out(out), Internal(false) {}
 
   static bool isIgnored(unsigned DiagID) {
     // FIXME: This feels like a hack.
@@ -71,12 +60,11 @@
     out.indent(Indent * 2);
 
     if (enabledByDefault(Group))
-      setColor(llvm::raw_ostream::GREEN);
+      out << Colors::GREEN;
     else
-      setColor(llvm::raw_ostream::YELLOW);
+      out << Colors::YELLOW;
 
-    out << "-W" << Group.getName() << "\n";
-    resetColor();
+    out << "-W" << Group.getName() << "\n" << Colors::RESET;
 
     ++Indent;
     for (const GroupRecord &GR : Group.subgroups()) {
@@ -85,12 +73,10 @@
 
     if (Internal) {
       for (const DiagnosticRecord &DR : Group.diagnostics()) {
-        if (ShowColors && !isIgnored(DR.DiagID))
-          setColor(llvm::raw_ostream::GREEN);
+        if (!isIgnored(DR.DiagID))
+          out << Colors::GREEN;
         out.indent(Indent * 2);
-        out << DR.getName();
-        resetColor();
-        out << "\n";
+        out << DR.getName() << Colors::RESET << "\n";
       }
     }
   }
@@ -136,13 +122,8 @@
   }
 
   void showKey() {
-    if (ShowColors) {
-      out << '\n';
-      setColor(llvm::raw_ostream::GREEN);
-      out << "GREEN";
-      resetColor();
-      out << " = enabled by default\n\n";
-    }
+    out << '\n' << Colors::GREEN << "GREEN" << Colors::RESET
+        << " = enabled by default\n\n";
   }
 };
 
@@ -182,6 +163,9 @@
     return -1;
   }
 
+  if (!hasColors(out))
+    out.enable_colors(false);
+
   TreePrinter TP(out);
   TP.Internal = Internal;
   TP.showKey();