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