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