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