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