T = {4->2, 4->6, 2->1, 2->3, 6->5, 6->7};
Manipulate[
TreePlot[T, Automatic, 4, EdgeRenderingFunction->({If[First[#2]===6 , Red, Black],Arrow[#1,0.1]}&),VertexRenderingFunction->({EdgeForm[Black], If[#2===a , Red,White], Disk[#1, 0.1], Black, Text[#2, #1]}&)], {a, 1, 7, 1}]

T2 = {{0, 0, 0, 0, 0, 0, 0}, {1, 0, 1, 0, 0, 0, 0}, {0, 0, 0, 0, 0, 0, 0}, {0, 1, 0, 0, 0, 1, 0}, {0, 0, 0, 0, 0, 0, 0}, {0, 0, 0, 0, 1, 0, 1}, {0, 0, 0, 0, 0, 0, 0}};
TreePlot[T2, Automatic, 4, EdgeRenderingFunction->({If[First[#2]===6 , Red, Black],Arrow[#1,0.1]}&),VertexRenderingFunction->({EdgeForm[Black], If[#2===3 , Red,White], Disk[#1, 0.1], Black, Text[#2, #1]}&)]

Position[Position[T2, 1], 4]