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