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)(27,35,36,39)(28,31,29,33)(32,37,40,38)(1,2)(3,5)(4,6)(7,8)(10,15)(12,13)(16,22)(17,18)(19,21)(23,24)(26,31)(28,29)(32,39)(33,34)(35,40)(37,38) involution — undirected(1,3,4,7)(2,5,6,8)(9,11,14,20)(10,16,18,24)(12,21,13,19)(15,22,17,23)(25,27)(26,32)(28,38)(29,37)(30,36)(31,39)(33,35)(34,40)(2,6)(5,8)(9,12,14,13)(10,17,18,15)(11,19,20,21)(16,22,24,23)(27,36)(32,40)(35,39)(37,38)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.