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