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