What if Neo took the blue pill AND the red pill??
What would have happened then??
0.o
Having the effects they do, taking both pills would mean the red pill would prevail cause it consists of the truth.
It's only possible to move forward with the blue pill, cause by default Mr. Anderson was already on the blue pill.
Then it all comes down to the beholders "choice" which would be an internal battle between Truth and Ignorance, while knowing both sides of the fence.
They aren't actually pills. They are packets of code smuggled in from off the server, somehow. Seeing as how they are code, one apparently resets his memory and life goes on as "normal" in the Matrix (blue), or some sort of premature "eject" sequence pulls him out of the Matrix with his mind intact (red). Like lines of code, perhaps it would matter in what precise order the pills were taken. Perhaps it could reset his memory and then still manage to eject him, since there's nothing specifying that either pill is the "antidote" of the other, therefore not ultimately or directly interfering with the function of the other. Again, perhaps the order would matter in this.