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