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