glutInitContextVersion(4, 0) no response to shader #version400

Hi, i have a problem when I use #version 400 shader with glutInitContextVersion(4, 0), my glClearColor(0.0, 0.0, 0.0, 0.0);
the screen is black; but when I change to glutInitContextVersion(3, 3), the screen display the right thing, I can’t undetstand this problem