  Triangulation graph staining is sufficient for planar graph staining. This
article will focus on triangulation and the nature of the color change channel
of the staining tool. By construction, the four colors of the vertex are
converted into three colors of the side, and two colors of the triangle.
Thereby the equivalent dyeing scheme is combined. The color change channel
utilizes the transferability of edge dyeing to reflect the integrity of the
triangulation graph. According to the nature of the color change channel, two
constraints are obtained, so that the color change can be followed regularly.
Eventually, a breakthrough was made in the structure of the reduced d(v)=5,
which proves the reducible of this structure. This negates the existence of the
smallest counterexample.
