glutPostRedisplay question

The InitInstance function of my program creates a window using glutCreateWindow, then calls glutDisplayFunc to call a callback function named “MyPaint” which draws a white square inside the window.

I want to be able to redraw anything inside the window, including the square and perhaps make it blue in color.

How do I do this? My existing code in InitInstance looks like this:

glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
glutInitWindowSize (450,450);
glutCreateWindow (“CDTI Display”);
glutDisplayFunc(MyPaint); //this
// draws a white
// square

    return TRUE;

Any help is deeply appreciated.