Fix Windows colors (#833)

* Fix Windows colors and update README.md

2 files changed, 4 insertions, 5 deletions

diff --git a/README.md b/README.md
index 7d168a1ed..5f7fa745c 100644
--- a/README.md
+++ b/README.md
@@ -131,9 +131,9 @@ You should see something like this:
 
 ![example output](https://raw.github.com/WebAssembly/wasm-emscripten/master/media/example.png)
 
-On Linux and Mac you should see pretty colors as in that image. Set `COLORS=0` in the env to disable colors if you prefer that. Set `COLORS=1` in the env to force colors (useful when piping to `more`, for example).
+By default you should see pretty colors as in that image. Set `COLORS=0` in the env to disable colors if you prefer that. On Linux and Mac, you can set `COLORS=1` in the env to force colors (useful when piping to `more`, for example). For Windows, pretty colors are only available when `stdout/stderr` are not redirected/piped.
 
-Pass `--debug` on the command line to see debug info, about asm.js functions as they are parsed, etc. `--debug=2` will show even more info.
+Pass `--debug` on the command line to see debug info, about asm.js functions as they are parsed, etc.
 
 ### C/C++ Source ⇒ asm2wasm ⇒ WebAssembly
 
diff --git a/src/support/colors.cpp b/src/support/colors.cpp
index 9a3b04f70..7d78306e0 100644
--- a/src/support/colors.cpp
+++ b/src/support/colors.cpp
@@ -43,9 +43,8 @@ void Colors::outputColorCode(std::ostream& stream, const char* colorCode) {
 
 void Colors::outputColorCode(std::ostream&stream, const WORD &colorCode) {
   const static bool has_color = []() {
-    return (getenv("COLORS") && getenv("COLORS")[0] == '1') ||  // forced
-           (_isatty(_fileno(stdout)) &&
-            (!getenv("COLORS") || getenv("COLORS")[0] != '0'));  // implicit
+    return _isatty(_fileno(stdout)) &&
+            (!getenv("COLORS") || getenv("COLORS")[0] != '0');  // implicit
   }();
   static HANDLE hStdout = GetStdHandle(STD_OUTPUT_HANDLE);
   static HANDLE hStderr = GetStdHandle(STD_ERROR_HANDLE);