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