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