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