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