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