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