  Le-diagrams are combinatorial objects that parametrize cells of the totally
nonnegative Grassmannian, called positroid cells, and each Le-diagram gives
rise to a cluster algebra which is believed to be isomorphic to the coordinate
ring of the corresponding positroid variety. We study quivers arising from
these diagrams and show that they can be constructed from the well-behaved
quivers associated to Grassmannians by deleting and merging certain vertices.
Then, we prove that quivers coming from arbitrary Le-diagrams, and more
generally reduced plabic graphs, admit a particular sequence of mutations
called a green-to-red sequence.
