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