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