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