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