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