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