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)(11,14)(12,15)(13,17)(16,20)(18,22)(19,21)(23,24)(25,26)(27,33)(28,31)(29,32)(30,36)(34,38)(35,40)(37,39) involution — undirected(2,5)(6,7)(9,11)(10,14)(12,19)(13,18)(15,21)(16,23)(17,22)(20,24)(25,27,34,35,28,36,29,37)(26,30,38,39,31,33,32,40)(10,15)(12,20)(14,21)(16,17)(19,24)(22,23)(27,35)(29,34)(30,39)(32,38)(33,40)(36,37) involution — undirected(1,3,4,8)(2,6,5,7)(11,18)(14,22)(19,24)(21,23)(26,31)(27,36)(32,38)(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.