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