I don't think you can have two cars there at the same time. It is not about if there is enough space at all. The lane is for right turn only and unless there were two lanes marked out for turning right, you can not have two cars making the turn together. So only one car can stay there waiting for turning.
So if there is no blue, the yellow one can drive up to the line without giving way to the green. But if the blue one is there, the yellow cannot squeeze into the lane that has already been taken up by the blue car.
However, the green car should always wait for the yellow one and the red one.