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