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)(11,16,18,12)(13,21,23,17)(19,20,24,22)(25,26)(27,31)(28,29)(30,33)(32,36)(34,35)(37,40)(38,39)(3,7)(5,8)(10,15)(12,16)(17,21)(20,22)(25,27)(26,31)(28,34)(29,35)(30,36)(32,33)(37,38)(39,40) involution — undirected(1,2)(3,5)(4,6)(7,8)(10,15)(11,18)(17,21)(19,24)(25,27,30,36)(26,31,33,32)(28,34,38,37)(29,35,39,40)(9,11,14,18)(10,16,15,12)(13,19,23,24)(17,22,21,20)(25,27)(26,32)(28,37)(29,35)(30,36)(31,33)(34,38)(39,40)(1,3)(2,5)(4,7)(6,8)(9,12,14,16)(10,11,15,18)(13,22,23,20)(17,24,21,19)(25,28,30,38)(26,29,33,39)(27,34,36,37)(31,35,32,40)(1,2)(3,5)(4,6)(7,8)(9,13,14,23)(10,17,15,21)(11,19,18,24)(12,20,16,22)(25,29)(26,28)(27,35)(30,39)(31,34)(32,37)(33,38)(36,40)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.