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