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