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