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