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