Index: include/clang/Frontend/CompilerInvocation.h
===================================================================
--- include/clang/Frontend/CompilerInvocation.h
+++ include/clang/Frontend/CompilerInvocation.h
@@ -47,7 +47,8 @@
 /// When errors are encountered, return false and, if Diags is non-null,
 /// report the error(s).
 bool ParseDiagnosticArgs(DiagnosticOptions &Opts, llvm::opt::ArgList &Args,
-                         DiagnosticsEngine *Diags = nullptr);
+                         DiagnosticsEngine *Diags = nullptr,
+                         bool DefaultDiagColor = true);
 
 class CompilerInvocationBase : public RefCountedBase<CompilerInvocation> {
   void operator=(const CompilerInvocationBase &) = delete;
Index: lib/Driver/Tools.cpp
===================================================================
--- lib/Driver/Tools.cpp
+++ lib/Driver/Tools.cpp
@@ -5529,43 +5529,27 @@
       CmdArgs.push_back("-fno-diagnostics-show-note-include-stack");
   }
 
-  // Color diagnostics are the default, unless the terminal doesn't support
-  // them.
-  // Support both clang's -f[no-]color-diagnostics and gcc's
-  // -f[no-]diagnostics-colors[=never|always|auto].
-  enum { Colors_On, Colors_Off, Colors_Auto } ShowColors = Colors_Auto;
-  for (const auto &Arg : Args) {
-    const Option &O = Arg->getOption();
+  // Color diagnostics are parsed by the driver directly from argv
+  // and later re-parsed to construct this job; claim any possible
+  // color diagnostic here to avoid warn_drv_unused_argument and
+  // diagnose bad OPT_fdiagnostics_color_EQ values.
+  for (Arg *A : Args) {
+    const Option &O = A->getOption();
     if (!O.matches(options::OPT_fcolor_diagnostics) &&
         !O.matches(options::OPT_fdiagnostics_color) &&
         !O.matches(options::OPT_fno_color_diagnostics) &&
         !O.matches(options::OPT_fno_diagnostics_color) &&
         !O.matches(options::OPT_fdiagnostics_color_EQ))
       continue;
-
-    Arg->claim();
-    if (O.matches(options::OPT_fcolor_diagnostics) ||
-        O.matches(options::OPT_fdiagnostics_color)) {
-      ShowColors = Colors_On;
-    } else if (O.matches(options::OPT_fno_color_diagnostics) ||
-               O.matches(options::OPT_fno_diagnostics_color)) {
-      ShowColors = Colors_Off;
-    } else {
-      assert(O.matches(options::OPT_fdiagnostics_color_EQ));
-      StringRef value(Arg->getValue());
-      if (value == "always")
-        ShowColors = Colors_On;
-      else if (value == "never")
-        ShowColors = Colors_Off;
-      else if (value == "auto")
-        ShowColors = Colors_Auto;
-      else
+    if (O.matches(options::OPT_fdiagnostics_color_EQ)) {
+      StringRef Value(A->getValue());
+      if (Value != "always" && Value != "never" && Value != "auto")
         getToolChain().getDriver().Diag(diag::err_drv_clang_unsupported)
-            << ("-fdiagnostics-color=" + value).str();
+              << ("-fdiagnostics-color=" + Value).str();
     }
+    A->claim();
   }
-  if (ShowColors == Colors_On ||
-      (ShowColors == Colors_Auto && llvm::sys::Process::StandardErrHasColors()))
+  if (D.getDiags().getDiagnosticOptions().ShowColors)
     CmdArgs.push_back("-fcolor-diagnostics");
 
   if (Args.hasArg(options::OPT_fansi_escape_codes))
Index: lib/Frontend/CompilerInvocation.cpp
===================================================================
--- lib/Frontend/CompilerInvocation.cpp
+++ lib/Frontend/CompilerInvocation.cpp
@@ -855,8 +855,51 @@
                         ModuleFiles.end());
 }
 
+static bool parseShowColorsArgs(const ArgList &Args, bool DefaultColor) {
+  // Color diagnostics default to auto ("on" if terminal supports) in the driver
+  // but default to off in cc1, needing an explicit OPT_fdiagnostics_color.
+  // Support both clang's -f[no-]color-diagnostics and gcc's
+  // -f[no-]diagnostics-colors[=never|always|auto].
+  enum {
+    Colors_On,
+    Colors_Off,
+    Colors_Auto
+  } ShowColors = DefaultColor ? Colors_Auto : Colors_Off;
+  for (Arg *A : Args) {
+    const Option &O = A->getOption();
+    if (!O.matches(options::OPT_fcolor_diagnostics) &&
+        !O.matches(options::OPT_fdiagnostics_color) &&
+        !O.matches(options::OPT_fno_color_diagnostics) &&
+        !O.matches(options::OPT_fno_diagnostics_color) &&
+        !O.matches(options::OPT_fdiagnostics_color_EQ))
+      continue;
+
+    if (O.matches(options::OPT_fcolor_diagnostics) ||
+        O.matches(options::OPT_fdiagnostics_color)) {
+      ShowColors = Colors_On;
+    } else if (O.matches(options::OPT_fno_color_diagnostics) ||
+               O.matches(options::OPT_fno_diagnostics_color)) {
+      ShowColors = Colors_Off;
+    } else {
+      assert(O.matches(options::OPT_fdiagnostics_color_EQ));
+      StringRef Value(A->getValue());
+      if (Value == "always")
+        ShowColors = Colors_On;
+      else if (Value == "never")
+        ShowColors = Colors_Off;
+      else if (Value == "auto")
+        ShowColors = Colors_Auto;
+    }
+  }
+  if (ShowColors == Colors_On ||
+      (ShowColors == Colors_Auto && llvm::sys::Process::StandardErrHasColors()))
+    return true;
+  return false;
+}
+
 bool clang::ParseDiagnosticArgs(DiagnosticOptions &Opts, ArgList &Args,
-                                DiagnosticsEngine *Diags) {
+                                DiagnosticsEngine *Diags,
+                                bool DefaultDiagColor) {
   using namespace options;
   bool Success = true;
 
@@ -869,7 +912,7 @@
   Opts.Pedantic = Args.hasArg(OPT_pedantic);
   Opts.PedanticErrors = Args.hasArg(OPT_pedantic_errors);
   Opts.ShowCarets = !Args.hasArg(OPT_fno_caret_diagnostics);
-  Opts.ShowColors = Args.hasArg(OPT_fcolor_diagnostics);
+  Opts.ShowColors = parseShowColorsArgs(Args, DefaultDiagColor);
   Opts.ShowColumn = Args.hasFlag(OPT_fshow_column,
                                  OPT_fno_show_column,
                                  /*Default=*/true);
@@ -2226,7 +2269,8 @@
   Success &= ParseAnalyzerArgs(*Res.getAnalyzerOpts(), Args, Diags);
   Success &= ParseMigratorArgs(Res.getMigratorOpts(), Args);
   ParseDependencyOutputArgs(Res.getDependencyOutputOpts(), Args);
-  Success &= ParseDiagnosticArgs(Res.getDiagnosticOpts(), Args, &Diags);
+  Success &= ParseDiagnosticArgs(Res.getDiagnosticOpts(), Args, &Diags,
+                                 false /*DefaultDiagColor*/);
   ParseCommentArgs(LangOpts.CommentOpts, Args);
   ParseFileSystemArgs(Res.getFileSystemOpts(), Args);
   // FIXME: We shouldn't have to pass the DashX option around here