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