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