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