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