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