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