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