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