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