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