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