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