If you’ve got lighting enabled, glColor does nothing, you must manipulate the colour of the object by changing its material properties.
However, you can still use glColor by using colormaterial:-
Why do you call glColor3f(1.0, 1.0, 0.0) between your vertices? You would get only yellow polygons this way, because AFAIK with flat shading the color of the last vertex determines the color of the whole polygon. Or you might get color interpolation between your color and yellow if you activate smooth shading.