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