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