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