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