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