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