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