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