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