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