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