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