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