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