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?

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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.