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