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