One vertex per element, one color per generator, with an edge from x to x·s.
(1,2)(3,6)(4,7)(5,8)(9,10)(11,17)(12,20)(13,15)(14,18)(16,21)(19,22)(23,24)(26,31)(27,34)(28,30)(32,39)(35,36)(38,40) involution — undirected(3,4)(6,7)(9,11)(10,14)(12,19)(13,18)(15,17)(16,22)(20,23)(21,24)(25,26)(27,32)(28,37)(29,31)(30,33)(34,40)(35,39)(36,38) involution — undirected(1,3,5,4)(2,6,8,7)(25,27,29,36)(26,32,31,38)(28,34,30,35)(33,39,37,40)(1,4,5,3)(2,7,8,6)(10,15)(11,18)(16,20)(19,24)(25,26)(27,32)(28,37)(29,31)(30,33)(34,40)(35,39)(36,38)(2,8)(6,7)(9,12,13,21)(10,16,15,20)(11,19,18,24)(14,22,17,23)(25,28,29,30)(26,33,31,37)(27,35,36,34)(32,40,38,39)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.