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