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