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