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