OpenGL: inaccurate color?

glColor3ui(0x80000000, 0, 0xFF000000);

glColor3ui(0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF);

glColor3ui(0xFF000000, 0xFF000000, 0xFF000000);

In either event, you'll need to ensure that any state that could
affect the final color has been disabled. The following code will
accomplish this:

glDisable (GL_BLEND); glDisable (GL_DITHER);
glDisable (GL_FOG); glDisable (GL_LIGHTING);
glDisable (GL_TEXTURE_1D); glDisable (GL_TEXTURE_2D);
glDisable (GL_TEXTURE_3D); glShadeModel (GL_FLAT);