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