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