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