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