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