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