I think it is how you have your control declared in the constructor. If you added the SimpleOpenGlControl to the form then the constructor code you are using is pointing to a new reference not the one in the controls collection. If I use the code below I get a white background and it looks like a fuscia colored square. As I suspected Gl variable is a static class in the library...
As you see in the form2_load method I am generating a new object of SimpleOpenGlControl, initializing its context and then adding a handler to the paint event and finally adding the control to the forms control collection. I am not familiar with the OpenGL libraries so cannot give you any advice on drawing, but at least this will show you what you expected to see previously (although I am filling with white instead of black in the glClearColor method)...
public partial class Form2 : Form
private void Form2_Load(object sender, EventArgs e)
Tao.Platform.Windows.SimpleOpenGlControl gl = new Tao.Platform.Windows.SimpleOpenGlControl();
gl.Paint += new PaintEventHandler(gl_Paint);
void gl_Paint(object sender, PaintEventArgs e)
Gl.glClearColor(255.0f, 255.0f, 255.0f, 255.0f);
Gl.glColor3f(1.0f, 0.0f, 1.0f);
Gl.glVertex3f(0.25f, 0.25f, 0.0f);
Gl.glVertex3f(0.75f, 0.25f, 0.0f);
Gl.glVertex3f(0.75f, 0.75f, 0.0f);
Gl.glVertex3f(0.25f, 0.75f, 0.25f);