I don't agree the light is either red or yellow, can I ask red-lighers and yellow-lighters alike one question - what, hypothetically, must happen for the light to turn green again?
Now, to Matthew's question, I am a "green-lighter" in the sense that I think the Society is and will remain for the forseeable future the best place on the planet to receive the Sacraments, to pass on the Faith to your children etc. I personally cannot understand how at least after the Jun 27, 2013 declaration of the Three Bishops, the light can be other than green. That declaration clearly condemns all and each of the Conciliar errors, not only religious liberty, the "subsistit in" ecclesiology, false ecuмenism and collegiality and also reiterates clearly why the New Mass was, is and remains unacceptable to the Society.
Anyone who reads that declaration, which is the publicly declared and official position of the Society, and then still claims that this is only the indult position is just frankly kidding himself. And then some. I do not know whether to laugh or to cry. It is not.
In any case, if the "red-lighters" want to claim Bishop Fellay's openness to an eventual canonical normalization when either the Pope has fully converted, or converted to such an extent that he fully acknowledges the rights of Tradition (point 11, Jun 27, 2013 Declaration) somehow not only excuses us from our binding duty to partake at Mass every Sunday, but even inexplicably imposes the opposite as an objective obligation, then, consider the following.
Recently, Bishop Williamson - correctly and against Fr. Pfeiffer's misunderstanding of the principles involved - clearly said that if Pope Francis were to give him a formal approval to continue doing everything His Excellency is doing right now, "I'd be on the next plane to Rome, I'd be on the next plane to Rome!" to get that approval.
Now, as a matter of fact, Bishop Williamson is only saying what Archbishop Lefebvre said, and is perfectly correct to say it. Therefore, it is right and just for the Society to also be ready and willing to accept Roman approval, if the Pope converts to such a point where he is ready and willing to give a formal approval for the Society to continue to do everything it is doing now. But according to Red-lighters, this would be not only a prudential mistake, but even a grave doctrinal error.
Now, because Bishop Williamson said such a thing, red lighters should either revisit their position, or if they do not wish to, then, to be consistent, ought also to "boycott" all Bishop Williamson's Masses for the same reason. And that's not all. To take your argument one step further, reductio ad absurdum, you ought, furthermore, to also "boycott" the Masses of all who remain affiliated with Bishop Williamson, for the same reason you now want to do that with every priest of the Society.
Otherwise, you might engage in "communicatio in sacris."
I'm sure this is going to be criticized, but I personally believe the Red light position is a sin, objectively. Say what you like, but the truth is that you have not even the slightest right, neither objectively nor subjectively, to excuse yourself from the obligation of attending Mass on Sunday, if you have a Society chapel near you, whoever does that is needlessly losing many priceless graces.