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