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