One vertex per element, one color per generator, with an edge from x to x·s.
(2,6)(3,4)(7,8)(9,10)(11,15)(12,20)(13,17)(14,19)(16,22)(18,24)(21,23)(27,33)(28,35)(30,37)(32,39)(34,36)(38,40) involution — undirected(1,2,5,8)(3,6,4,7)(9,11)(10,14)(12,21)(13,18)(15,20)(16,24)(17,23)(19,22)(25,26)(27,30)(28,32)(29,31)(33,37)(34,38)(35,39)(36,40)(3,4)(6,7)(9,11)(10,15)(12,19)(13,18)(14,20)(16,23)(17,24)(21,22)(25,27,29,34)(26,30,31,38)(28,36,35,33)(32,40,39,37)(1,3,5,4)(2,7,8,6)(11,18)(14,23)(15,24)(19,21)(26,31)(30,38)(32,39)(37,40)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.