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