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)(11,17)(12,15)(13,18)(14,26)(16,19)(20,23)(21,32)(22,33)(24,31)(25,30)(27,34)(28,35)(29,39)(36,37)(38,40) involution — undirected(2,5)(3,7)(9,11,16,23)(10,17,19,20)(12,24,26,33)(13,27,28,40)(14,22,15,31)(18,34,35,38)(21,29,37,30)(25,32,39,36)(9,12,14,10,16,26,15,19)(11,20,31,33,23,17,22,24)(13,25,29,18,28,39,30,35)(21,36,40,34,37,32,27,38)(2,5)(6,8)(13,28)(18,35)(21,37)(25,39)(27,40)(29,30)(32,36)(34,38) involution — undirected(1,3,4,7)(2,6,5,8)(9,13,15,30,16,28,14,29)(10,18,12,25,19,35,26,39)(11,21,22,27,23,37,31,40)(17,32,33,34,20,36,24,38)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.