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