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