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