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