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