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