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