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