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