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