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