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