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