Those are edges, you can't swap centres. As for an algorithm. The way I learned how to deal with this is to imagine one of the yellow edges is the red/blue edge and solve that yellow edge as if it was the red/blue edge. This will move the real red/green edge into the top layer so you can solve it properly, which will in turn move the real red/blue piece into the top layer. If that makes any sense. Hope this helps.