force gcc colors

CMakeLists.txt

@@ -179,6 +179,7 @@ if(CMAKE_CXX_COMPILER_ID MATCHES "Clang")
     set(CLANG ON)
 elseif(CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
     set(GCC ON)
+    string(APPEND CMAKE_CXX_FLAGS " -fdiagnostics-color=always")
 elseif(NOT WIN32)
     message(FATAL_ERROR "Unsupported compiler, id=${CMAKE_CXX_COMPILER_ID}")
 endif()