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