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