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