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