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