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