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