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