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