OpenGL: glLogicOp() color filling trick with different coloring?

I am currently using glLogicOp() with a cube, which i render twice: with glFrontFace(GL_CW) and then with glFron开发者_如何学CtFace(GL_CCW). This allows me to see which area of the other 3d object my cube is overlapping with.

But i want to change the negative color to something else, lets say 0.5f transparent blue color.

How this can be done? Sorry about the title, i dont know the name of this method.

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Also, i am having problem with being inside the cube with my camera: i need to fill the screen with negative coloring, is there any other way than swithing to 2d mode and drawing a quad with glLogicOp() enabled ? Also the problem is that theres a chance to see bugged rendering if i am at the edge of the cube surface, any ideas for preventing this perfectly?

You should look into the "Carmack's reverse" algorithm and the stencil shadow algorithms in general, as your problem is closely related to them (your cube being a shadow volume object). You will not get away with using glLogicOp() if you want other colors than black and white.