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