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