One vertex per element, one color per generator, with an edge from x to x·s.
(1,2)(3,6)(4,5)(7,8)(9,10)(11,14)(12,15)(13,16)(17,21)(18,22)(19,23)(20,24)(25,26)(27,38)(28,40)(29,34)(30,37)(31,36)(32,35)(33,39) involution — undirected(2,5)(3,7)(9,11)(10,14)(12,19)(13,18)(15,23)(16,22)(17,20)(21,24)(25,27,31,39)(26,33,36,38)(28,30,29,32)(34,37,40,35)(9,12,13,20)(10,15,16,24)(11,17,18,19)(14,21,22,23)(25,28,31,29)(26,33,36,38)(27,30,39,32)(34,35,40,37)(1,3,4,7)(2,6,5,8)(10,16)(11,18)(15,24)(17,19)(25,29,31,28)(26,34,36,40)(27,30,39,32)(33,35,38,37)(2,5)(6,8)(11,18)(14,22)(17,19)(21,23)(25,30,31,32)(26,35,36,37)(27,28,39,29)(33,40,38,34)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.