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