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