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)(11,23)(12,18)(13,19)(14,20)(15,21)(16,22)(17,27)(24,35)(25,32)(26,34)(28,38)(29,40)(30,36)(31,37)(33,39)(9,11)(10,17)(12,29)(13,24)(14,26)(15,27)(16,28)(18,35)(19,32)(20,23)(21,38)(22,34)(25,31)(30,39)(33,37)(36,40) involution — undirected(1,3,4,8)(2,5,6,7)(9,12,15,13,16,31,14,30)(10,18,21,19,22,37,20,36)(11,24,26,29,28,39,27,25)(17,32,23,35,34,40,38,33)(9,13,15,31,16,30,14,12)(10,19,21,37,22,36,20,18)(11,25,26,24,28,29,27,39)(17,33,23,32,34,35,38,40)(9,14,16,15)(10,20,22,21)(11,26,28,27)(12,30,31,13)(17,23,34,38)(18,36,37,19)(24,29,39,25)(32,35,40,33)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.