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