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