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