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