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