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