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