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