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