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)(12,15)(13,16)(17,21)(18,22)(19,23)(20,24)(26,32)(27,33)(29,30)(34,35)(36,37)(39,40) involution — undirected(1,3,5,4)(2,6,7,8)(9,11)(10,14)(12,19)(13,17)(15,23)(16,21)(18,20)(22,24)(25,26,30,35,31,34,29,32)(27,28,33,40,37,38,36,39)(11,17)(14,21)(18,19)(22,23)(25,27,30,33,31,37,29,36)(26,28,35,40,34,38,32,39)(9,12,13,20)(10,15,16,24)(11,18,17,19)(14,22,21,23)(25,28)(26,33)(27,32)(29,39)(30,40)(31,38)(34,36)(35,37)(1,4,5,3)(2,6,7,8)(10,16)(14,21)(15,24)(22,23)(26,34)(28,38)(32,35)(39,40)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.