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