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