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