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)(11,20)(12,23)(13,19)(14,18)(15,17)(16,22)(21,24)(25,26)(27,33)(28,30)(29,37)(31,36)(32,35)(34,39)(38,40) involution — undirected(1,3,4,8)(2,5,6,7)(9,11)(10,16)(12,15)(13,21)(14,22)(17,24)(18,20)(19,23)(26,30)(27,34)(29,35)(31,38)(9,12,15,22,14,21,13,11)(10,16,19,23,18,20,17,24)(25,27,35,40,28,34,29,36)(26,31,37,39,30,38,32,33)(2,6)(5,7)(9,13,14,15)(10,17,18,19)(11,21,22,12)(16,24,20,23)(26,30)(31,38)(32,37)(33,39)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.