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