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