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