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