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