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