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