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