OpenGL Performance Become Super slow after intense color drawing

I have used OpenGl to draw 2D and 3D graph. 2D graph uses lots of Colors. If I open 2D window first, then switch to 3D graph window, then my 3D object rotation become really slow, there is at least several seconds delay between mouse move and object rotation. But if I go to 3D window first, then every thing works fine.Is this normal with OpenGL? did anyone have the same problem before? Can anyone please tell me what is the problem? Thanks alot…