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