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