When I draw things in 3D perspective, which contains green lighting, it bleeds into my 2D ortho drawings.
In this picture, I draw my 3d scene on the large left-side viewport, and draw my 2d scene on the smaller right-side viewport(which contains a 2d red triangle):
(you can see the full red triangle has been tainted with green colors from previous 3d drawings)
This is my drawing structure:
//start 3d drawing
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glViewport(0, 0, windowWidth/1.3, windowHeight);
glClearColor(0,0.5,0.5,0);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(60.0, (float)windowWidth / (float)windowHeight, 0.4, 9000.0);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glEnable(GL_DEPTH_TEST);
glEnable(GL_LIGHTING);
glEnable(GL_LIGHT0);
glEnable(GL_NORMALIZE);
glEnable(GL_COLOR_MATERIAL);
//draw 3d primitives + model and view transforms
//2D drawing
glClear(GL_DEPTH_BUFFER_BIT);
glViewport(windowWidth/1.3, 0, windowWidth, windowHeight);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(0.0f, windowWidth, windowHeight, 0.0f, 0.0f, 1.0f);
glDisable(GL_DEPTH_TEST);
glDisable(GL_CULL_FACE);
glDisable(GL_TEXTURE_2D);
glDisable(GL_LIGHTING);
//draw red triangle
glPushMatrix();
glColor3f(1.0f, 0.0f, 0.0f);
glBegin(GL_TRIANGLES);
glVertex3f(0.0f, 0.0f, 0.0f);
glVertex3f(20.0f, 20.0f, 0.0f);
glVertex3f(70.0f, 20.0f, 0.0f);
glEnd();
glPopMatrix();
//swap buffers
glutSwapBuffers();